For KDE, Valve found it easier to work with KDE devs than GNOME devs.

Your xrandr script is missing output monitor. Try this

COMMAND=/usr/bin/xrandr --ouput LVDS1 --rotate normal

If LVDS1 is incorrect. You can check the output by running xrandr.

https://wiki.archlinux.org/title/Xrandr#Scripts

KDE Neon is rolling release for DE. So it’s pretty much couple days waiting once Plasma 6 released or just instantly released.

You can always change the icons, Get new icons.... from the icons setting page. Theme in KDE is very easy to change.

Example
Theme: https://github.com/catppuccin/kde
Icon: https://store.kde.org/p/1340791

People who use Arch and just want GUI is asking for troubles sooner or later. It’s Arch so you will have to deal with the Terminal somewhere along the line.

EndeavourOS has a welcome page that list all the common operations you need and you just need to click it.

Instead of Manjaro, try EndeavourOS, easy Arch install with GUI.