The Riff Raffs will do your Angus, Page and Clapton stuff no problem. As for high gain/heavy riffing, I think it depends what style you mean - they'll do heavy in a stoner/doom kind of way. 70s heavy, basically. If you want Pantera, Lamb Of God, anything "modern", I'm no expert on that stuff but I don't
think the Riff Raffs will go there.
The Rebel Yell's a bright but "big" sounding pickup. It's versatile, but it always has a lot of punch and presence, it definitely won't mush out. If you played ONLY classic rock or ONLY heavier stuff, I don't think it would be the first choice for either. But it might be the best all-rounder for a mahogany guitar.
I haven't tried Crawlers but I definitely want a set, just not sure what guitar they'll go in. I know they're voiced to work in either Strats or Les Pauls, but I think the maple cap of an LP makes a difference - they
might mush out in an SG, I don't know.
Dunno what else to say really. Tim's comments in
this thread are really useful, if you haven't seen them already.