I think this video might be helpful
By “pure C++” I mean that you literally do everything in code, including layouts, arranging controls, assigning resources, binding events, handling animations, etc.
Can you do it in UMG with code? Probaly yes, but, well… UMG is created exactly in order to not to do it by hand 
I know UMG is easier, but to be honest all this UObject bloat attached to everything, even a little static text label is too much for me (yeah, i know, typical cpp paranoid :D)