I don't usually have my browser set to fullscreen and instead have the window set to around 65% of my screen's total width and about 70% of my screen's total height, which lets me easily watch YouTube videos on one window while browsing the web on a separate window, leaving space to have notepad documents and other stuff open to the sides. It's kinda hard to explain, so I'll include a screenshot below:
I guess I got so used to having my windows sized and placed this way that it's become second nature for me. Having anything in fullscreen mode (besides videos, of course) feels
super weird for me.
Because of this, I've had to set Fakku! to 80% zoom instead and that works just fine for me. The text is a little small, but it isn't that big of a deal because I'm on a laptop that's only a foot away from my face.