Depending on your transcoding needs you might not even need it for that.

I have a proxbox with a R5 4600G even under extreme loads the stock cooler is fine. Honestly once prox is setup you don’t need a GPU. The video output of proxmox is just a terminal (Debian) so as long as things are running normally you can do everything through the web interface even without the gpu. I do highly recommend a second GPU (either a G series CPU or a cheap GPU) if you want to try proxmox GPU passthrough. I’ve done it and can say it is extremely difficult to get working reliably with just a single GPU.

I’ll freely admit to skimming a bit but yes proxmox can run trunas inside of it. Proxmox is powerful but might be a little frustrating to learn at first. For example by default proxmox expects to use the boot drive for itself and it’s not immediately clear how to change that to use that disk for other things.

The noctua dh-15 is overkill for that cpu btw unless you’re doing an overclock which I wouldn’t recommend for server use. What’s your plans for the 1060? If using proxmox you’ll want to get one of the “G” series AMD CPUs do that proxmox binds to the apu and then you should be able to do gpu passthrough on the 1060.