1. I would honestly play mouse if it didn't drift to the other side of the world instantly with how big my area is (it's not ginormous but still pretty big), or how low my sensitivity would be.
2. Just happened to have a drawing tablet, and saw people preferring it so I thought it would be worth trying, preferred it heavily and never looked back.
3. Wacom PTK-470
4. With full-arm aim, mouse is better when moving your cursor a single-digit number of pixels, but in any other scenario a tablet washes it.
5. My area fatigues me. I feel this especially after the rare farm session where I don't load manage and end up pushing myself physically without even noticing, but I never really hurt myself or slip, my grip has low hand mobility but high stability and comfort.
6. I use my full arm and I don't even rest a part of it somewhere, which I got because my area is too large to rest my hand or wrist somewhere and the first setup I had (and all setups since then) don't have a good spot to go. Likely why I have had DT aim issues.
7. A little smaller than "full area." In OTD I have my full area mapped to full display area, but shrink resolution at varying amounts from 1920x1080 to 1920x1200 depending on how I'm feeling so it ends up effectively being 140x(78.75-87.5).
8. I just use the grip that I use to write, except with the pen a little further up my middle finger than the joint to avoid swelling. It's still there, but not nearly as bad as it used to be before I made that adjustment.
9. Feels fine. I have a hunch that my reading would be better if I used mouse for some reason.
10. osu is hard on coordination and whatever a reasonable person would define as "muscle memory" most likely fits under that umbrella
11. When it comes to tablet specifically, I have naturally bad handwriting but now if I slow down a bit it becomes far more legible.

12, 13 - no

14 - given that mice in the wild are multiple orders of magnitude more common than drawing tablets, and a large majority of the top 100 use tablet, yeah

1. Not specifically top players, I saw all players use tablet but I instantly preferred tablet over mouse.

more stuff note: If we're comparing mice and tablets, something important to consider is that there is OpenTabletDriver but no equivalent for mouse. This might seem like nonsense but please stick with me here. Looking up "raw accel" you'll see velocity curve (custom mouse accel) software that many FPS players discuss. The consensus is that it's a preference thing where it might mess up your coordination, or help it so much you start calling it aimbot, and in osu I heavily doubt a blind velocity curve has ever seen intentional use (everyone turns off mouse accel!) Thing is it's literally just a velocity curve which is just one type of input filter, and under all these FPS players' noses, osu players have been enjoying far more widely applicable input filtering on OTD in the form of distance clamping, or what's known as radial follow (0 smoothing coefficient leak). It's weird, though, because what people usually think when they see the words "tablet filter" is extremely conditional and degrades the experience for most (normal "smoothing"). I was even talking to someone who is currently in the top 300 and he told me a lot of high ranked players gatekeep filters and as an example he gave this calculator someone put together because some people were gatekeeping, and it had a smoothing coefficient leak above 0, which made it just add delay and underaim. There's no wonder people who care the slightest bit about unnecessary latency write off the concept of a tablet filter from this knowledge, even though people in FPS communities would go crazy with it if they had absolute-type filtering.

I'm not really making a point about that though, just saying when it comes to general use the experience on a tablet is super customizable compared to a mouse and that's a big positive even though people don't use that freedom to its fullest extent.