kcm-wacomtablet is a package that depends on plasma-workspace so when you installed that, sddm was installed too from the lost list of dependencies … hence you had two Dysplay Managers, and none can start because of the other. When you uninstalled lightdm probably also removed other packages that make XFCE work, whyle by installing lxdm you had no proper switch to it, but also sddm was still trying to load in the same time with lxdm …
You have to follow the LXDM Configuration - Manjaro
A quick search in the forum about xfce and UI configurator for tablet, would have revealed you at least this
Mixing DEs on the same user is always a bad idea without knowing the implications and how to avoid trouble.