Automatically pair the same set of Bluetooth Devices, while booting MACOS from 2 independent partitions:

(Each partition contains the whole MACOS)

IMHO: Better, Alternative Solution, if you please:

The real, hardware MAC Address is a randomly generated, practically globally unique number baked into each communication device's ROM, so it can be only changed in your system by swapping that device for another one. In fact, my best advice to you is spend a little over $2 on a brand new USB Bluetooth 5.0 transmitter(/receiver) dongle, or 2 of them, and all you need to do is use one for each of your setups. As a free bonus, depending on your current Bluetooth version, this cheap solution would give you all the nice Bluetooth 5.0, 4.x, 3.x,... features.

Nah, let's just do it anyway (because we can?):

I presume that your partitions both contain the entire MACOS, and they do not share any system storage space. I recommend simply to:

1. Setup all the Bluetooth devices after booting with partition 1.
2. Copy the ~/Library/Preferences/com.apple.Bluetooth.plist file to a USB drive.
3. Boot from partition 2.
4. Replace the partition 2 ~/Library/Preferences/com.apple.Bluetooth.plist with the file from the USB drive.

Let me know if this worked out for you.

Automatically pair the same set of Bluetooth Devices, while booting MACOS from 2 independent partitions:

(Each partition contains the whole MACOS)

Use identical Bluetooth.plist file on multiple partitions:

I presume that your partitions both contain the entire MACOS, and they do not share any system storage space. I recommend simply to:

1. Setup all the Bluetooth devices after booting with partition 1.
2. Copy the ~/Library/Preferences/com.apple.Bluetooth.plist file to a USB drive.
3. Boot from partition 2.
4. Replace the partition 2 ~/Library/Preferences/com.apple.Bluetooth.plist with the file from the USB drive.

Let me know if this worked out for you.

To Change some MAC Address on MACOS:

IMHO: Better, Alternative Solution, if you please:

The real, hardware MAC Address is a randomly generated, practically globally unique number baked into each communication device's ROM, so it can be only changed in your system by swapping that device for another one. In fact, my best advice to you is spend a little over $2 on a brand new USB Bluetooth 5.0 transmitter(/receiver) dongle, or 2 of them, and all you need to do is use one for each of your setups. As a free bonus, depending on your current Bluetooth version, this cheap solution would give you all the nice Bluetooth 5.0, 4.x, 3.x,... features.

Nah, let's just do it anyway (because we can?):

If you however still want to play with spoofing, please read on. In many cases, system manufactures allow spoofing, or software-based reassigning of hardware MAC addresses. This is how it can be accomplished in MACOS:

1. Be careful! Changing Hardware IDs like: MAC address (Media Access Control address) can lead to unexpected side effects, depending on your system and user software configurations. You may, for example loose the ability to use certain software that uses MAC address for unique licensing.
2. Always record your current configuration using email, message, printout or other means, so the later viewing does not depend on the system you are currently changing. In Terminal, enter the command networksetup -listallhardwareports that should give you output similar to this:

$ networksetup -listallhardwareports

Hardware Port: Ethernet
Device: en0
Ethernet Address: c4:ff:ff:0c:cc:2a

    # ... other devices may be listed on your system here ...

Hardware Port: Bluetooth PAN
Device: en2
Ethernet Address: 60:ff:4b:07:ff:e8

Repeating this JIC: Copy the output from Terminal, and persist it, so you can easily retrieve it later, in case you would desire to undo the changes. (Email / Message / Printout...)

3. Pick the interface that you want to change the MAC address for from your Terminal output from step 2, and use the ifconfig <Interface> ether XX:XX:XX:XX:XX:XX command in Terminal to make the change. So theoretically, to increase the Bluetooth MAC address from my listing by 1, the command should be: ifconfig en2 ether 60:ff:4b:07:ff:e9 - this would unfortunately most likely result in following system reply: ifconfig: interface en2 does not exist - not what we desired...

Automatically pair the same set of Bluetooth Devices, while booting MACOS from 2 independent partitions:

(Each partition contains the whole MACOS)

IMHO: Better, Alternative Solution, if you please:

The real, hardware MAC Address is a randomly generated, practically globally unique number baked into each communication device's ROM, so it can be only changed in your system by swapping that device for another one. In fact, my best advice to you is spend a little over $2 on a brand new USB Bluetooth 5.0 transmitter(/receiver) dongle, or 2 of them, and all you need to do is use one for each of your setups. As a free bonus, depending on your current Bluetooth version, this cheap solution would give you all the nice Bluetooth 5.0, 4.x, 3.x,... features.

Nah, let's just do it anyway (because we can?):

I presume that your partitions both contain the entire MACOS, and they do not share any system storage space. I recommend simply to:

1. Setup all the Bluetooth devices after booting with partition 1.
2. Copy the ~/Library/Preferences/com.apple.Bluetooth.plist file to a USB drive.
3. Boot from partition 2.
4. Replace the partition 2 ~/Library/Preferences/com.apple.Bluetooth.plist with the file from the USB drive.

Let me know if this worked out for you.

To Change some MAC Address on MACOS:

1. Be careful! Changing Hardware IDs like: MAC address (Media Access Control address) can lead to unexpected side effects, depending on your system and user software configurations. You may, for example loose the ability to use certain software that uses MAC address for unique licensing.
2. Always record your current configuration using email, message, printout or other means, so the later viewing does not depend on the system you are currently changing. In Terminal enter the command networksetup -listallhardwareports that should give you output similar to this:

$ networksetup -listallhardwareports

Hardware Port: Ethernet
Device: en0
Ethernet Address: c4:ff:ff:0c:cc:2a

Hardware Port: FireWire
Device: fw0
Ethernet Address: e8:ff:88:ff:fe:e0:ff:b6

Hardware Port: Wi-Fi
Device: en1
Ethernet Address: 60:ff:4b:07:ff:08

Hardware Port: Bluetooth PAN
Device: en2
Ethernet Address: 60:ff:4b:07:ff:e8

Repeating this JIC: Copy the output from Terminal, and persist it, so you can easily retrieve it later, in case you would desire to undo the changes. (Email / Message / Printout...)

3. Pick the interface that you want to change the MAC address for from your Terminal output from step 2, and use the ifconfig <Interface> ether XX:XX:XX:XX:XX:XX command in Terminal to make the change.

To Change some MAC Address on MACOS:

IMHO: Better, Alternative Solution, if you please:

The real, hardware MAC Address is a randomly generated, practically globally unique number baked into each communication device's ROM, so it can be only changed in your system by swapping that device for another one. In fact, my best advice to you is spend a little over $2 on a brand new USB Bluetooth 5.0 transmitter(/receiver) dongle, or 2 of them, and all you need to do is use one for each of your setups. As a free bonus, depending on your current Bluetooth version, this cheap solution would give you all the nice Bluetooth 5.0, 4.x, 3.x,... features.

Nah, let's just do it anyway (because we can?):

If you however still want to play with spoofing, please read on. In many cases, system manufactures allow spoofing, or software-based reassigning of hardware MAC addresses. This is how it can be accomplished in MACOS:

1. Be careful! Changing Hardware IDs like: MAC address (Media Access Control address) can lead to unexpected side effects, depending on your system and user software configurations. You may, for example loose the ability to use certain software that uses MAC address for unique licensing.
2. Always record your current configuration using email, message, printout or other means, so the later viewing does not depend on the system you are currently changing. In Terminal, enter the command networksetup -listallhardwareports that should give you output similar to this:

$ networksetup -listallhardwareports

Hardware Port: Ethernet
Device: en0
Ethernet Address: c4:ff:ff:0c:cc:2a

    # ... other devices may be listed on your system here ...

Hardware Port: Bluetooth PAN
Device: en2
Ethernet Address: 60:ff:4b:07:ff:e8

Repeating this JIC: Copy the output from Terminal, and persist it, so you can easily retrieve it later, in case you would desire to undo the changes. (Email / Message / Printout...)

3. Pick the interface that you want to change the MAC address for from your Terminal output from step 2, and use the ifconfig <Interface> ether XX:XX:XX:XX:XX:XX command in Terminal to make the change. So theoretically, to increase the Bluetooth MAC address from my listing by 1, the command should be: ifconfig en2 ether 60:ff:4b:07:ff:e9 - this would unfortunately most likely result in following system reply: ifconfig: interface en2 does not exist - not what we desired...