1. It can me milled so the optic will not be too high. You can use a dovetail mount with your red dot if you want but it’ll be too high. If you only use it for range plinking, it’ll suffice. I have mine milled by Primary Machine for use in USPSA.
2. RMR is a type of red dot made by trijicon. When you say RMR, I think you’re talking about red dots. Again, if for range plinking, by the cheapest you can afford. If for home defense, I recommend Trijicon’s RMR. For competition, I recommend Delta Point Pro, sig Romeo 3Max or 3XL, C-more RTS2 etc.
3. CGW, CZC and Primary Machine.