There is a possible issue with the CL and large lenses
One issue I've had with my Leica CL is that the with really "rotund" lenses, the focusing ring blocks part or all of the rangefinder window (the small one). This effectively negates focusing using the rangefinder or at least impedes it. I have a CV 35mm F1.2 and put one of those rubber ring tabs on it and I can't use it on the Leica CL for reason mentioned above.
I've seen the CV 21 and it looks really big. Might be a non issue but thought I'd point it out!