Red dots and LPVOs on the shelf, AR furniture from the brands people actually ask for, and a bench to put it on for you.
Red dots and LPVOs.
If you're stuck between a red dot and a holographic for the same rifle, ask before you buy. It usually comes down to what you're doing with the gun and whether you have astigmatism, and it's a two-minute conversation at the counter that saves people a few hundred dollars fairly often.
Stocks, grips, handguards, the parts that actually get swapped.
Want it put on rather than doing it at the kitchen table? That's the bench, and basic installs are usually same day.