Next month my home club has a multi-gun USPSA match and I want to try the 3 gun that is run locally to me so I obviously need a rifle.

I have a home defense/hurricane/looter/zombie M4orgery that is set and I am not going to tinker with but like any competitive shooter I've got other stuff too. Looking at the list below how would you suggest I set up a multi gun rifle just starting out. There are obviously some new toys I would like but thing like bunk beds and snowblowers are getting in the way of fun.

Upper: Stag arms upper with a precision reflex carbon fiber handguard/low profile gas block and 16 inch 1:9 carbine length barrel with a YHM muzzle break. <---This is the constant

Lowers:

Std lower with Rifle buffer tube, Magpul MOE rifle stock and MOE+ grip with a RRA 2 stage trigger
Std lower with carbine adjustable buffer tube, std M4 stock and MOE grip with a mil-spec trigger

Optics:
Magpul BUIS
Vortex 3-9
Redfield 2-7
Eotech
Aimpoint h-1

The multigun is going to be a bay match with at most 100yd rifle shots. I am also not opposed to moving a trigger between lowers.

Thanks for your help and while I know there is bigger and better out there its what I have and don't want to go balls deep if I find its not for me.

2 stage trigger w/Magpul furniture.  If there may be targets beyond 150yds, I'd go with the 2-7 optic.  If not, then go aimpoint.

Generally, multigun ARs get a few things:

Accurate barrel
High quality trigger
Extended free float tube
Low power variable optic
Muzzle break/compensator

Everything else is to enhance reliability or for operator preference.