Mainboard:
MSI Meg Unify X570 (hab gehört, mit MSI Boards, soll es im aktuellen OS Probleme geben?)
CPU:
Ryzen 5950X
Motherboard is very good but with 5950x you are limited to Big Sur
If you choose a 3950x you can use it with old motherboard firmware also in macOS Ventura
MSI not advised better to choose Asus or AsRock (x570 Steel legend is good and cheaper)
Check well internal ethernet support with any motherboard you will choose because from Monterey and greater OS could be a pain to have it working well
It depends if you use app for video editing or SFX you could have the need of more ram (64Gb)
I use different kind of nvme, an old Samsung 960 pro (1Tb), 2 Sabrent rocket 4.0 with 0 problems from High Sierra to Ventura
I would not suggest to use this "beast" with Proxmox if you do not need special 32 bit apps or virtualisation apps because kernel patches are solid and all apps could work fine in bare metal