Xwayland title bars are too large
I run GNOME Wayland on Fedora 30. XWayland applications have a way too big window title bar: I have a dual display setup. One regular display at 100% scaling, one hidpi display at 150% scaling. The size of the menu bar varies per XWayland application, but the font is sometimes also way too big.
The Signal application from the image above is installed from a flatpak.
xorg-x11-server-Xwayland.x86_64 1.20.5-3.fc30 gnome-session-wayland-session.x86_64 3.32.0-1.fc30