Don't shoot a lot of USPSA these days but when I do it's single stack because it's the next best thing to revolver which really is dead. Plenty enough guys in my area still play in SS to make it interesting including one GM and several Masters.
I run DAA mag pouches bullets out because even though I have plenty ample waist, real estate on the belt is just easier.
Safariland USPSA Kit (wouldn't bother if I was doing it over) with a 5197 holster.
Non-rail SA TRP for major, STI Trojan for minor.
Alphas are easier and quicker with minor. Stage design plays into it, but all the big boys at the big matches always seem to run major. Minor is like rimfire, it's almost cheating.