Elevator and rudder seal using tape will be fine on the flat fabric covered surfaces (Sub, Champ, T-craft etc.) . You can do that with little fear of it changing or ruining some flight characteristic. FAA ramp checks are another issue. In that event, I would position it as preventing water from causing corrosion, rather than an air seal.

Real "Frise" ailerons (I always thought it was Friese but Wikipedia says no) can be sealed this way because there is still a piano type hinge at the top. You would just put the tape on the inside (under surface) of the gap.

But the "slotted" ailerons that have a curved leading edge on the aileron, and a matching curved "cove" on the trailing edge of the wing... are different. You can and probably will decrease aileron authority at one position or another. There is a reasonable chance that putting the VG's on the leading edge of the wing will give you enough additional low speed authority, to allow you to seal off the slot on a slotted aileron without losing much roll control at low speed, but I have not seen that proven out on an actual airplane.

With any of the "regular" ailerons, you can certainly experiment with seals (cautiously) without any horrible fear of an uncontrollable airplane. It might get sluggish or soft (Taylorcraft known for this), but you surely will still be able to control the airplane.

With the completely separate Junkers type ailerons (Kitfox, CH-701, British Auster) it is not a "leaking gap" in the bad sense of the word so you are not needing to "seal" it..