I have a 2017 5K iMac running Mojave 10.14.6. It has a 2 TB Fusion drive internally formatted as HFS+. FileVault is not enabled, but I wish to do so. Will the disk have its format changed to APFS if I enable FileVault?
My recollection is that the disk was originally formatted as HFS+ from the factory and when I turned on FileVault, the format changed to APFS. Granted that was over a year ago, so I could be very off-base.
I want to prevent going to APFS again. The performance degraded to dismal levels. Now that I have reformatted as HFS+, it is surprisingly speedy.