First let me disclose I don't shoot 3gun. Don't have time to do much 1gun as it is.
If the scope is for long range, the red dot for short, then I don't see the need for variable zoom. Problem is, and why I'm chiming in, is that fixed power scopes are real limited. Many companies dropped out of making quality, fixed power scopes (other than 4x). Seems the market was demanding variables. I was lucky to get one of the Nikon Monarch 6x before they were discontinued. Leoupold and S&B still make good FP scopes, but some of them cost more than my guns.
So my very unqualified opinion is, if the scope is just for long distances, I'd put a fixed power scope somewhere in the 8x range. Easy to pick up the target, but strong enough to be sure of your aimpoint.