A mix for me. Muscle-memory tells me when to do a lot of things - I always clip the cast of my mount for example by starting to move before it finishes on-screen, for example.
Even if you spam hard you should not get carpal tunnel unless your playing area is not set up correctly. If you begin to feel the symptoms of it (one of the best earlier indicators being numbness in fingertips and so on, even if the actual problem ends up being in the wrist), you seriously need to take a hard look at the chair, table, keyboard, mouse and so on, and particularly how you're sitting at them. If, like a lot of players, you're slumped/hunched (you see this in some streamers, even), playing at a table that's just at "whatever" height, and your mouse/keyboard just positioned in a way that "seems to fit", you're are BEGGING for carpal tunnel. Begging for it.
There's tons of online guides to this stuff, and for 90% of people, following the same instructions as working at an office typing all day, you'll prevent any chance of carpal tunnel as well as back problems (i.e. right posture, right desk and monitor height, right size of mouse, with a proper grip, arms at your sides not splayed out and so on). There are some people who may need to do more, due to predispositions (genetic or injury-based), or because they're playing such lengthy hours or whatever. Really helps if you take breaks, too - doesn't really have to be 15 ever 45, but at least 5 every hour or so is good, even if you just a walk a little circuit round your room or the like.
I say this because I've had and fixed both carpal tunnel and back problems from computer usage, and I've seen friends and co-workers who have failed to fix either, because they ignored this kind of thing, and just used bullshit "treatments" they found on the internet or painkillers or whatever, and some of them have ended up with permanent problems.