I use the KDE version, but technically you can install any desktop environment and switch between them on the login screen. So you can have multiple desktop environments as well if you want. The different version ISO are basically only for convenience.
Yes, Manjaro comes with a GUI package manager called pamac. So you technically never have to enter any commands for updates. It even gives you notifications for kernel updates.
Xfce comes with Mousepad as the default text editor. You can install gedit but I recommend that you use mousepad instead since it's much lighter.
Also, Manjaro does not use apt as the package manager. Like all Arch Linux based distros, it is based on pacman.
The command you need to enter is:
Alternatively, launch the package manager GUI application and search for the package you want to install.
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