using custom controls instead of user controls to create complex views

using custom controls instead of user controls to create complex views

I do not have enough information about WPF, so please correct me. It seems
that to handle different views create many usercontrols is needed(each
view needs one usercontol which binds to the viewModel) , and also by
using MVVM pattern designers can create views independently. now if the
designer tries to create two themes with different structure, he has to
create two usercontrols because when using usercontrols the layout is
specified(as mentioned here). on the other way customControls do not
specify the layout, so it seems that using CustomControls is more
reasonable. so the question: is using custom controls instead of
usercontrols is correct, and if it is, is it reasonable for viewmodels to
inherit from Control, and views become only styles for viewmodels?