I use F9 for my domestic commuting (I rather don't fly in a RJ even if its F, too many irr ops). They have a pretty good boarding procedure, first Summit (their highest level), then Ascent (2nd highest) with Classic Plus tickets and then they board by zone based on where you sit (back to front).
Works well for me and I always get to board first. On UA even being (still this year) GS it was extremely spotty and all over the place after the merger.