Pro GPU? - Gentoo (used) workstation build

[Zucca]

This is a bit like a continuation to my earlier topic of if I should choose dual CPU or not.

I chose to go with dual CPU. For the base, I bought a used Dell Precision Tower 7810.
This is good opportunity to learn the possible quirks of such system. I stuffed it with 8x32GB of RAM.
I also found a pair of Xeon E5-2697 V4s just for 70€ (about the same in USD). I'll install them later. It now has Xeon E5-2620v3s (Which I probably move to my server later... that's another story).

I plan to use at least two 4k displays with the workstation. I'll maybe add third display there (1600x1920).
I've been looking at used Radeon Pro GPUs, but also non-pro.

Now... If I buy, say Radeon W9100, will it work just fine with amdgpu drivers? Can I utilize GPGPU just like if it was a "consumer" GPU?

Any suggestions for a (better) gpu for my setup? PCIe in this workstation is 3.0 and the setup can generally accept a GPU of around 300W of power.
I don't want to fight with nvidia GPUs. I use wayland and it seems nvidia isn't there yet. I also don't like to use their closed source drivers. So the other ones would be Intel GPUs. But does my PCIe 3.0 bottleneck them?
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..: Zucca :..