There is a reason three gun shooters put the scope on top and the secondary optic off set to the side.
Scopes are used to engage longer range targets. When engaging longer range targets, small differences make big misses. You want your cheek weld to be as consistent as possible and the shot to be as natural as possible.
Using an offset iron sight, or red dot is for close in targets. Small differences don't make for misses.
Also consider that using an offset mount for your optic can put it in the way of your ejection port. Bouncing brass off of an optic isn't for me, either.
The trajectory weather you're shooting with a canted rifle or not is going to be the same. You just have to zero the rifle with the optic at the same angle to the bore as you intend to shoot it. Conventionally speaking, the optic should be directly over the bore of the rifle.