I agree Alf. Interchangeable "grips" and "grip panels" really are two different things.
Some 1911 grip panels will significantly change the feel but not as much as changing the entire grip would. I have a pair of 1911 grips that I haven't measured the thickness of but they must be thicker than average because it gives the grip a much rounder feel.
There are 1911 slim grips that will change the feel too but the trigger reach is going to close to the same no matter which grips you use, thin, standard, or thick. And changing mainspring housings makes nowhere near the difference of changing back-straps on pistols with truly interchangeable grips.