I've never had such good first layers. Replaced my warped ass Ender3S1 bed with a mirror.
I'm actually not afraid of printing things larger than a few square inches on the bed.... Waited way too long for this. Tightening up the eccentric screws on the bed carriage so it doesn't wobble also helps.
I swapped to glass a few years ago and the things I have learned since are that glass that's too thick will cause you issues with bed temperature, and you can print PETG on it so long as you can guarantee you'll be there when the print finishes to release it with IPA or you'll have chunks of glass missing from your build plate. I got a G10 build plate 2 days ago and sofar I'm liking it more than glass
A thin layer of glue stick kept petg from bonding to glass for me, but a nice thick layer of G10 is better as long as you heat soak it before printing. I roughed mine up with some sandpaper and haven't had any issues. Just remember good ppe when working with fiberglass.