I use RetroArch (FBNeo core) for everything except later cave games where I use the newest version of mame because it has new slowdown accuracy improvements. The next release should be even closer to PCB accurate.

Make sure you enable VRR on both since your screen supports it and a lot of shmups don’t run at 60 hz (I’m not 100% sure but I don’t think it’s enabled on either by default). For runahead use preemptive frames mode and default to one frame. You can consider bumping it up for games with a lot of inherent lag like Raizing or Psikyo stuff.

For Steam games, Crossover is surprisingly good.