When starting out with Arch Linux 5 years ago, choosing a desktop environment and/or window manager was one of the key decisions. i3's excellent documentation and principles[0] really sold it for me. The base config is full of sensible defaults and the learning curve for shortcuts was relatively short for me. I use it alone as my WM with picom as compositor (which is unnecessary) and no DE. I've never looked back and…
1. Per display xrandr settings, or xsettings
2. Statusbar losing tray icons when switching screens or reloading. Tray icons having the wrong size or not showing up at all. Part of the reason is that all tray icons used to be Xembed based. Then came appindicators with KDE having KStatusNotifierItems which may just be a Freedesktop StatusNotifierItem implementation. Polybar too frequently had this issue[0]. The only third party statusbar that properly implements this with using sni-proxy is a haskell based one which's name I forgot which is hard to use on Archlinux if you use the dynamically linked haskell packages.
My compromise right now is to use lxqt with i3, which seems to be a somewhat lightweight wrapper around xsettingsd and a lightweight session implementation.
I really prefer Awesome's tiling mechanism over i3, but i3's multiscreen just works. No weird window disappearing bugs etc.
A lot of these issues seem to have been fixed inside of Gnome directly or inside of KDE, but for some annoying reason every DE seems to have to solve these issues from scratch, which is just a standard Linux issue. I've been using linux as a DE for multiple decades now, so you'd think these issues would be fixed at a more fundamental level at some point, but no ...