Assuming pic 1, to correct the geometry at the control horn end and actually get pretty equal (mechanically set) throw when there is a modest height differential, you may need to shim the horn attach point with a wedge to make the horn holes (roughly) perpendicular to the rod.

I make little beveled plywood shims all the time to do this sort of geometry correction.

When the height difference is extreme (ex. Elevator on a T-Tail plane), it may make sense to introduce intermediate 90 degree bellcranks to attain the desired right(ish) angles.

People frequently introduce undesirable differential by simply bolting their horns to a tapered aileron with no shim angle corrections. When the horn and servo are bottom of wing mounted, the induced differential from that flat mounting on a tapered aileron will typically be causing slightly more mechanical down deflection than up even when the servo horn/rod are at a perfect 90 degree angle. More down deflection that up can promote a tip stall when you're low and slow at higher AOA.

[The exception here would be an undercambered wing where the aileron angle may be enough to pitch the aileron horn tip forward rather than rearward.]