Is the top bar a latte-dock bar or the newly migrated stuff?
If you were still using latte, you could disable the window bar for maximized windows via: Latte settings → (x) support for borderless maximized windows in different layouts
side note: I have no clue how this works, but in case you are not using latte, you can install it via sudo pacman -S latte-dock, then check that box, and you can boot latte off your system again. The change stays iirc. Might be hard to get the buttons back though if you forget how you did that