One advantage to being in a ban state is that you could put padding on your buffer tube without affecting its operation.
When it comes to the other questions there are others on this thread that are far more knowledgeable than I am but may not operate in a ban state.
If you are forced to go with reduced capacity magazines, I have found that 20 round P mags with the 10 round limiters and epoxied/riveted for "permanence" are the best option for neutered mags. They are about as reliable as you can get, large enough to allow you to grip them during mag changes, low profile enough to keep them out of the way during bench or prone shooting, and can be assembled for about $18 a pop. I source mine from 44mag.com where they specialize in disassembling them so they can be shipped to ban states.
As far as optics, I really like my Aimpoint PRO for a the excellent cost to performance value it has.