On top of all the normal things you may want out of a gaming mouse for any other FPS game (a shape that fits your hand/grip, extra buttons you need, lightweight, or anything else), MCSR benefits more from a couple specific features:
Being able to drag click is the first and most obvious added requirement, and even if you don’t plan on drag clicking, getting a mouse that is capable of extremely high CPS will also benefit butterfly clicking enough to be almost as good in most speedrunning situations compared to drag. Any mouse that has optical switches and a customizable debounce time should be able to drag in theory, but I would definitely try and hear what people who actually own the mouse have to say. Whether or not you need tape is a lot more personal, like it depends a lot on weather and how moist your finger is usually, but regardless most people who drag click consistently do use tape regardless of their mouse.
Another requirement would be being able to lower your DPI using a button. Part of this is a software thing, and most gaming mice should do this no problem (except Keychron kinda). As for having an extra physical button to change your DPI, that is a nice to have (and probably why the Burst II Air was so popular) but really isn’t necessary, since you can use middle click or one of the two side mouse buttons. That might require you to change your binds in game to accommodate, but I wouldn’t personally put any weight on having buttons other than the default 5. Or you can use Linux and this doesn’t matter because you don’t need to change DPI.
Other than those two things, MCSR doesn’t really require anything extra. I think it’s also important to mention that you may not need a mouse with a high CPS cap or easy DPI toggling, depending on your requirements and setup. Feinberg has a G502, Infume has a Razer Naga V2 HyperSpeed, bigbigmongey has a G203, etc etc. That being said, a lot of runners have an OP1 (edcr, beefsalad, v_strid, lowkey, silverr, nonsochiama), many have a Burst II Air (doogile, Ranik, Darvy), and a few have the Lamzu Atlantis (hax, Aquacorde, 7rowl), so there is clearly some value in getting one of these specific mice.
@sonya might have thoughts on this too