medium is fine, I mostly prefer 24'' monitors nowadays but I've used GAYMING monitors in the past ( Anus rog) with 27'' and higher res; and medium works fine.
Try the tablet on amazon; and return it if it doesn't work out for you then just find a larger Intuos in that case.
You could do the same with the Intuos if it's on amazon or bestbuy ( probably easier to return).
Try the xp pen deco pro first and see how it works out for you, and yeah 2 monitors are enough. It's mores how much you care about color accuracy, unless ur an industry professional rec 709/100% srgb isn't important but super nice to have.
Just a nice IPS panel with good colours will do fine.