Is there a way to make the models appear on your back/hip like in FO3/FNV?

Sort of. The only mod we are aware of that does this without needing patches or any additional modding, is Working Visible Weapons on the Nexus.

Unfortunately for Xbox users, there is no mod that we are aware of that accomplishes this. The above-linked mod is available on PC only, as it requires Fallout 4 Script Extender and Mod Configuration Menu.