I think many here misunderstood your intention. The combination of "server" and "what DE?" is a weird thing for most of us, especially since you said headless, which usually means no desktop, only ssh and stuff.
But I think I understand what you are up to.
You want something mainly for gaming, where the PC acts as "brain" of the games, and you only stream them to a low-power device, similar to what Stadia was planned. Right?
For that, I'll recommend Bazzite with Moonlight or how it's called.
Bazzite is a gaming oriented Fedora Atomic spin that has Nvidia-drivers already baked in, updates itself (you only need to reboot once in a while) and gives you a great experience, even offering to boot straight into Steam's BPM.
Moonlight/ Sunshine/ whatever is a screen sharing protocol or software that allows you to stream games without latency or much quality loss.
I'm no pro tho, so take my suggestions with a grain of salt :)