Currently there doesn't appear to be a way to disable the adjustments made to the font for tooltips. The config has a toggle called "Style Tooltips" that implies it'll stop changing the fonts if I turn it off, but this doesn't seem to be working properly.

Here's a tooltop in Vanilla WoW with no addons (with the interface settings showing to prove that there are no other addons loaded):

Here is the exact same tooltip, with only Improved Blizzard UI loaded, and all the tooltip options toggled off:

Hopefully this is unintended behavior, but if not could we please have the option to disable all tooltip changes made by this addon?

Thank you for this report. I'm going to be taking a pass through the entire UI and clearing up these config issues.