An option to consider if you haven’t already, for an AR pistol (depending on if and how you plan on toting it around) is the Law folder. It’s a nice piece of kit that allows you to transport and store your firearm in smaller bags etc but still be quickly deployable as opposed to having it broken down into separate upper/lower. In my opinion your “shtf” rifle/pistol should be something you are able to and will easily grab to throw in your car when you leave the house every time, and not cause unnecessary attention. As far as optic goes just pick something you like and and are comfortable with. If you want fast and lite go with an Aimpoint or eotech, if you think you may want a Lpvo get one and try it out. Wait around for a good deal on something used, give it a shot and resell it if it’s not your thing. I find that no matter how many people’s opinions I read about some things, I really am not satisfied until I get some firsthand experience to see/decide for myself sometimes.