Is adding second GPU card worth speeding up Final Cut Pro?

[GDS]

Someone speak about me?

short answer: not worth it

long answer:
I work on Davinci (not FCPX) but we can consider same approach as DaVinci is well known to be optimized on Mac OS

so the good point:
Metal is well used on both cards when it is about rendering, I saw a good reduction of time for a video shot in 8k and with timeline 4k with some effects, GPU monitoring shows a use of 80% each on rendering

the "not so good point":
I didn't see any advantages concerning effects, filters and so on when I work on my project, and the GPU monitoring didn't show the second card used at more than few % when working live on a project

My 2cts:
not interesting at all if it is for video / photo / 3D etc
it asks too much power (2x GPU) the PSU needs to be enough rock solid (I have a 1500W and sometimes the PC shut down for no reason, since I pulled out one GPU: no more shut down)
and the interest to have 2 GPUs are pretty limited in time (only rendering for example)

possible solution:
the interest could be to use a second GPU (not as the 6800XT, a middle range one) to use for driving your screen/screens and let the 6800XT focusing on the background tasks


i sent one of my 6900XT WC to have money back

I am not able to answer but I remember a couple of posts, for example this one. Check also GDS, he says he runs two 6900 XTs; they might give you some hints