OK, here are some of (my) thoughts:
1.) What is a RRA?
2.) Magnification depends on the sight picture you are personally comfortable with (or, with which you are personally comfortable--if this is an English test
Up to about 16X (variable scope, of course) is adequate and desirable for most shooters, except for perhaps for over 800 yrds, then more magnification is desirable; again, if you feel comfortable with it.