Described as the Smash of Warhammer. Not necessarily completely left-field, but the campaigns aren't canon, as whichever race you play as fights all others, and should defeat them. So obviously non-canonical.

Length isn't too crazy for an RTS. This'd be a good entry point for that genre.

Don't worry about the previous installments. No continuing storyline, the third game seems to be the only one with any story anyways. Story lies in your personal campaign conquering other races, choices you make, allies you get, etc... Besides III should have everything in 2 and 1 anyways.