Longer wheelbase and wider track yield less weight transfer.
Track I'd run as wide as rules allow while still being able to pick good lines and get around the track.
Wheelbase, longer = more stable. Depends on what kind of track you're going to be running at, speeds, steer angle range, that sort of thing. Tight, low to medium speed auto-x, short wheelbase. Silverstone, much longer.
Grip is a four letter word.
2 is the new #1.