I remember that i found Tibia to be rather cpu-demanding for a 2D-tilebased game, when trying it back some years. However I can't recall any details. I just remember that during the years that i played it, i tried both - the windows-version with wine as well as the Linux-version. Still it's worth a try.
Would it in theory bring a slightly better result to run qemu with the Linux-version within a qemu-Linux-environment instead of running it within Windows95/98? Not sure.
Anyway ... after playing it for more than 10 (with some breaks) years for free, I am happy to have (hopefully) beaten it the only way you can beat the game 2 years and 6 days ago (Last login: May 02 2010, 14:56:49 CEST) -> I stopped playing it. The greed-focused majority of players and the (virtual-)materialistic-game-developments of CIP (the producer) helped me with that.