Funny thing, because one of the Assassin's Creed games years ago - probably Black Flag or Unity - was dropping framerate on the default setting, and google told me "maximum performance" fixed it, and it did.
So I figured hey it makes sense to use GPU to its fullest, right? And never thought about it, because I never expected this setting to affect power consumption in idle as well.
Fucking Ubisoft, I swear..
Of course, I reran some benchmarks now (Cyberpunk, Kingdom Come, RDR2) and the "normal" setting gives me the same exact performance as "maximum performance" (actually in Cyberpunk I had 2fps extra with normal).