Greetings Folks!
In Windows 11 all applications that are opened use the complete Laptop screen.
There is no need to increase the font size in the Brave Browser.
Hope my statement makes sense???
To open all applications maximized you can use this gnome-extension:
Install extension manager and then browse for the extension to install it.
Applications often remember the last window size. In other words, if you maximize the window and then close it, the next time you open it, the window should open in maximized mode.