What are the differences for using different versions of SDK for different cards? I think you are supposed to use 2.1 for older cards, and 2.4 for the ones that don't support it, correct?

Is there a "tag" manual/tutorial anywhere? Is there a list of tags and what they do?
By tags I mean things like -v -w -f and the number after them. I see some people say "use aggression size 12!" but I have no idea what that means/how to do it.
Right now I have -v -w 256, and I don't know if I'm supposed to add/take out tags, or add numbers or...yeah. Confused :/