Close approximate conversions are:
2.75 = 70mm
4.10 = 105mm
The 80/90 by 21 front will give you very similar overall diameter, meaning the speedo will read very close to true.
The 110 and 120 rears in either 80 or 90 % profile will fit and be fine. The 90 profiles are slightly taller, so will gear the bike up a little, dropping the engine revs for the same speed. In theory, the 90 profile will also last a little longer. Is that a good thing or bad? Only you can say.
These bikes are not fussy about tire sizes. I have had 130 rears on and there was no problem with the handling.
Hope this helps.
Nigel in NZ
The mouth of a perfectly contented man is filled with .
-- 2200 BC Egyptian inscription