To an extent, yes. The oldest Windows game that I'd still probably want to play legitimately is probably Thief: The Dark Project, from 1998. It was made for DirectX version 6. Naturally, it will just not run on modern systems, Windows or Linux.

There are patches that bring it to DX9. It has an internal frame rate limiter to something weird, 90 fps or something. The weakest machine I have available can push that about at 4K while apparently still in full energy saving mode.

Proton's DX9 emulation is apparently a bit rough, but most of the DX9 games you'd want to emulate are just fine with 'brute force'. There's a couple of problematic games - CS:GO, for instance - where the efficiency matters.