In this 4.14 cycle the main goal was to port all core components to Gtk3 (over Gtk2) and GDBus (over D-Bus GLib). Most components also received GObject Introspection support. Along the way we ended up polishing our user experience, introducing quite a few new features and improvements (read below) and fixings a boatload of bugs (read changelog).
A lot of focus seems to have been on HiDPI support, which, in 2019, is probably a good thing. Multimonitor support received quite a bit of love, too, as did other display-related things like colour profiles, display scaling, and so on.
That’s just a selection though, so be sure to read through all the changes.
Does anyone tested it on slow PC? How does performance compare to older version? Does gtk3 is more hungry of CPU?
From my experience, GTK+3 application are, in fact, more CPU and memory hungry than GTK+2. Of course, this is probably due to additional features in the new version.
My main concern resources-wise, however, is their move towards using GObject introspection. Trying to figure out what an object can and cannot due at runtime is inherently slower than doing so at compile time. Xfce hasn’t really been useful on older computers for quite a long time, though. In my opinion, it currently serves a niche for people who do not like GNOME3’s workflow and prefer the good old menu, tray, etc.
I use Xfce on a daily basis under MX Linux, it is quite peppy on an AMD A8 APU. I would never dare put it on my Semprom 3000+ laptop with 736MB of RAM, though. Even LXDE has a hard time on it.
Finally! Waited a long time for this release.