Most 68K apps that will work on a graphics card are as stable as they are on 3.9.
If something proves to be a little unstable you can force it run on the interpreted emulation, Photogenics for example become much more stable when you do thus.
There are also a couple of utilities on OS4 Depot such as CIAgent and Blitzen which can help coax a few more programs into running.
Most old ECS and AGA games are going to have to be run under EUAE.
I find it good enough that I use my other A1 as my main everyday system here.
