I use a 43" 4k tv at the standard non-retina 4k with an m1 pro. I tried your 8k supersampling but it doesn't seem to improve on the default 4:4:4 8bit rgb non-retina for me. (smoother but not as crisp outside terminals?)

The TV is unusable without BetterDisplay because the apple default negotiation preference. I hope waydabber can figure something out with you.