If I install xfce4 offline, is it à full install with everything?
It is a solid and working starting point.
It does not have everything out of the box, but practically anything you’d probably like to add later is available.
What particular features or packages do you have in mind?
Almost forgot: offline install means it is not up to date right after install, so you’ll need to update first using terminal command:
sudo pacman -Syu
What do you mean by “everything”? Is there something specific you’re looking for, or do you just mean everything to make xfce function??