I have optics on all of my ARs. I use the Burris P.E.P.R mount on two of them. Works well, IMO.
As for an optic, I've got a couple of Vortex scopes and don't buy anything else anymore. Just put one on my 6.5 Grendel AR. Vortex makes a 2-7x35 in their
Diamondback line if that is the power you are looking for. I have a Diamondback HP on one of my ARs.