Lighter I won't entirely disagree with: I think a default install of KDE will still be heavier than Xfce, but GTK3 isn't the lightest toolkit, and you can slim

Lighter I won't entirely disagree with: I think a default install of KDE will still be heavier than Xfce, but GTK3 isn't the lightest toolkit, and you can slim KDE down without losing much functionality. But I don't get the HiDPI point? Certainly 4.16 had issues with HiDPI, but in 4.18 you can set the UI scaling factor, and I believe shortly before and/or after initial release, we fixed up all the issues of blurry image rendering. I have a HiDPI screen and it's worked very well for me, and looks nice.