do you ever play like a grandmaster for a few games and then play like 100 elo for a few

ACPL will always vary from game to game because sometimes you're on good form and sometimes bad form, sometimes your opponent makes an early blunder, sometimes the game gets into complex positions and sometimes it stays relatively simple. For instance, on a good day when I'm focusing, I often get an ACPL under 15, but then sometimes I get into a confusing position, end up in time trouble, I'm tired, etc. and my ACPL may rise as high as 50 or even sometimes 70.