Do rcs perform well in the presence of high aerodynamic forces?
RCS of any sort loses ISP in atmosphere, and thus thrust, the same as any rocket engine (because that's all they are).
However they will only become completely ineffective if the apparent pressure on them is greater than their chamber pressure, which never happens.
What is more of a concern is sizing the RCS to be strong enough to overpower the sum of the aerodynamic forces on the vehicle, which can be huge.
Realistically, aerodynamically active surfaces are much more practical in the atmosphere. Whether they be fins, or gridfins, or static surfaces(wings) or dynamic surfaces like the Starship's , erm,... flaperons (or whatever they've settled on calling those things)
Example: the X-15 plane used aero surfaces for control while in enough atmosphere to do so, and only when so high that the air was too thin, did it rely on its RCS for control.