@yadid yeap there were compatibility problems between A500 and A600, but that was not most of the stuff. Probably due to a different kickstart and newer librairies. On RCB, i mainly use whdl roms and a few .adf. Most of the games & demos (i automatically exclude AGA softwares that are stocked in A1200 folder) run without changing the default configuration.
If you are a former Amiga user, i suggest you download whdl in .lha format and try them.
For info, the next RCB V7 uses a new version of Amiberry (and the mouse is at least optimizted), the GUI interface is clear and simple. P-uae is also avaible (i prefer amiberry although).