Re: Base and ring question(newbie)
Not sure what you are asking.
I think you are referring to a tapered picatinny base for zeroing at longer range.
If that is the case how much taper you need is also dependant on how much elevation adjustment you have in the scope.
Generally a 20- 25 MOA taper will get your zero out far enough to be able to correct for 800 to1000 drops in the average scope .
If you want to zero out further then go 30 MOA taper.
Parallax adjustment is important at any range but more so as it gets longer.
For long range shooting you usually need heavy powerful scopes so you can aim precisely at long range . Good rigid mounts that will not move or flex are the best option. Some kind of tactical rings like Badger Ordinance to fit the Picatinny rail , high enough so the objective housing clears the barrel would be good .