I haven’t had a good chance to thoroughly test, but early impressions in my current workflow that is heavy on Canon 1DX III 4K HEVC footage isn’t particularly promising.
A complex project with grading, sharpening and graphics is smooth on my M1 Mac mini, and choppy to the point of useless on my Mac Pro even with the 6900 XT.
I’m keen to see if there are any improvements as the 11.4 betas roll on and any updates to FCP, but it feels pretty crap that a 16-core system with excellent graphics can’t play a simple HEVC 10 bit 422 timeline when my fanless M1 Air can.