250 FPS? You don't need more than 60, you should enable the limiter in-game (arguably 120 if you have a 120hz monitor but IMO you don't need it for Tibia).
As far as it affecting FPS, I guess it makes sense, but I didn't notice a difference on my computer when running 5 clients at once all injected (didn't actually pull up the FPS though).
TLDR: 250 fps is likely more frames per second than your monitor is even capable of displaying