If I had a FireWire 400 DVD drive connected (via a FireWire 400-800 cable) to a FireWire 800 hard drive that was then connected via a Thunderbolt to FireWire 800 adapter to a Thunderbolt hard drive, that was then connected to a Mac, would I be able to use all the drives? And would I get Thunderbolt speeds on the Thunderbolt drive and FireWire 800 speeds on the FireWire drive? Also all the drives are powered externally.
Okay, It just dawned on me I have the hardware here to test daisy-chaining two FireWire devices at the end of the Thunderbolt daisy-chain and it did work. I have access to all devices in the chain, both Thunderbolt and FireWire. I could not test with FireWire devices in the middle of the chain as I'm short a cable/adapter for an in the middle configuration. However Apple has stated in the past the non-Thunderbold devices had to be at the end of the chain.
As to the throughput speed of the FireWire devices they cannot exceed what they're rated regardless of how connected.