Thanks for your review.
I had to build a custom UI to avoid some issues with the custom browser behavior. I'm working on re implementing these features in my custom UI again. Fullscreen will work in the next release, PiP and speed controls are planned. You will be able to select the controls, you want to see in the player bar via the extension-icon-menu.

Edit: I added a hotfix in v1.1.0: You can now right-click in between the control elements. Not the best solution, but is should help you until I'll implement more features.