Regarding game compatibility, I have hundreds of WHDLoad and JST games on my A1200 and A600 and the compatibility is very good. The A1200 is a bit better, because of the 020 allowing you to exit back to workbench on some installs. I haven't gotten around to trying all of my disk games yet because I'm spoiled by HD installs.
As for chip ram only, the stock A500 has chip only. I remember using degrader to turn off fast RAM for some old games that didn't expect it. So, I don't think that is the core problem.
