I have configurations set up for A500, A500+, A600, A1000, and A4000, and I have no problems running the gmes I already have. In all my configs, I didn't use 68EC020, since using the CPU, I get nothing but a blank screen. I don't know what games require fast ram.
One of the games I have, Arabian Nights, only require 1MB chip. No more, no less. I don't know what games require fast ram.