I got that off-brand classic controller I mentioned above and installed one of its new sticks into my controller a few days ago. I only replaced the mechanical parts; I didn't use the potentiometers that came with it, and instead used some spare official pots I had (they looked like they were better quality).
The new sticks in that classic controller are the old style -metal casing (I can post a picture of them if you'd like). Moving the stick from neutral to half way in any direction feels completely normal, but beyond that it feels like it has a little more resistance than original GC sticks (in particular, at least with the one I pulled out for my left stick, moving to the right beyond the half-way point feels like it's less smooth). But this feeling is very slight, and unnoticeable during play. I can't say that any technical mistakes while I've played with it were because of the joystick. A few rare times I've noticed that when trying to dashdance or run I've instead turned around or walked, but I can't be sure whether it's the stick, the used pots (though appearing to be in good condition (non-worn tracks)) I used, or just me. Ultimately I'd say those sticks are a good cheap fix.
However, to my great surprise, I've also found a shop that actually sells individual Wii/GC replacement joysticks! (It's a surprise to me because I've looked more than once before and have never found them.) They're here. They also sell replacement knobs.
The new sticks in that classic controller are the old style -metal casing (I can post a picture of them if you'd like). Moving the stick from neutral to half way in any direction feels completely normal, but beyond that it feels like it has a little more resistance than original GC sticks (in particular, at least with the one I pulled out for my left stick, moving to the right beyond the half-way point feels like it's less smooth). But this feeling is very slight, and unnoticeable during play. I can't say that any technical mistakes while I've played with it were because of the joystick. A few rare times I've noticed that when trying to dashdance or run I've instead turned around or walked, but I can't be sure whether it's the stick, the used pots (though appearing to be in good condition (non-worn tracks)) I used, or just me. Ultimately I'd say those sticks are a good cheap fix.
However, to my great surprise, I've also found a shop that actually sells individual Wii/GC replacement joysticks! (It's a surprise to me because I've looked more than once before and have never found them.) They're here. They also sell replacement knobs.