I haven't tested this much, but how much does UAE emulate the various processor speeds and how accurately?
In other words, how much of a difference does it make for emulation, between selecting a 68020 or 68040 f.x. other than some compatibility issues ?
It basically makes no difference if you select 020 or 040 as far as speed is concerned. People usually suggest using the 020 setting as there is more software specifically optimized for 020/030 as opposed to 040.
I happen to set everything up as 040 in my WinUAE environment years ago so I have just stuck with that, but speed wise it really is the same. i.e. you don't get "more" speed selecting 040.