The FPS over certain number who you can see in Tibia are FAKE. There is not limitation in the FPS number you can see in Tibia (If you have a NASA pc can get high numbers) BUT you dont gonna see a difference between 100 FPS and 1000 FPS, due the limitations of the game inself.
In other things the games have FPS limitations because even if the game can't reproduce 1000 FPS (But it show you that number, because dont have limitation) it force the graphic card to work more and can burn the cards. Recently the game New World have a problem with the limitation frames with graphic cards Zotac (If I remember properly) and the game just force the cards and it burn (It was fixed).