House models built inside unreal

I’ve built some houses and furniture using unreal’s moddling tools. I plan to use these houses in a game setting and want the player character to be able to go in/out of these buildings and have npc’s potentially living in them.

I’m trying to avoid using store bought assets where possible If I can build things myself, So my understanding of how these things work at runtime is limited.

Do I have to make separate interiors? Or can I just use the buildings I’ve made as is either merged into one structure or modular as they are now?