ReacOS is a testament to how solid were Windows 2000/XP's UI for everyday tasks. I wouldn't mind being back in a Windows env/shop with ReactOS.
I think you might enjoy Xfce from the GNU/Linux world.
https://www.opendesktop.org/p/1253201
With the Redmond or Chicago95 theme for GTK, those apps also look in place in case you need them.
For truly a low resource usage desktop I look at LXQt. Same base lib as KDE, namely Qt, which is apparently a lot lighter on the resources than GTK. Not sure if it is ready yet these days.