Recs.
Updated
Xfce is a low resource user friendly desktop environment created for UNIX-like operating systems.
SpecsUpdate
Pros
Pro Window manager (XFWM) is a compositing WM by default
By having a compositing WM as the default WM makes way for a lot of visual tweaks and tricks that can and do make Xfce look great. You can adjust the transparency, shadows, borders, etc. and many other advanced tweaks are also available.
Cons
Con Officially is no longer the champion of lightweight memory usage
According to multiple credible sources in the Linux world and the KDE developers, XFCE now uses more memory than Plasma 5.17, due to Plasma bringing better and faster updates. Even the XFCE folks admit XFCE is somewhat getting out of hand.
This was tested on a minimal install of Plasma, without the entire KDE ecosystem. So if you are concerned with memory usage and use a "build-it-yourself" distribution like Arch, avoid XFCE and install Plasma by itself.
Con Will become more interconnected an less modular
Isn't as modular anymore as it was 10 years ago. In the future (4.16) they will also introduce GTK Client Side Decorations to all setting dialogs so you will have some problems with using a different Window manager or when using xfce components outside of Xfce/GNOME.