If EnOS had originally set up lightdm, it would have used lightdm-slick-greeter as default and not lightdm-gtk-greeter. There is nothing wrong with lightdm-gtk-greeter, but slick-greeter is what was chosen as default for EnOS
.
If lightdm-slick-greeter is installed, in the EnOS repo, is a package
sudo pacman -Sy eos-settings-xfce4
Installing that package should set up the EnOS theming, but since sddm was originally installed that might mess with things. Go to
scroll down and notice there is a
eos-settings-xxxx
for every DE that is supported, plus the i3wm Window Manager.
There is also a Topic that covers basic theming, etc for lightdm-slick-greeter.
None of this is necessary, but it will give you something to tinker with. 
Pudge