best practices when building a level?

I’m building a level for a multiplayer… .
this level will have some bases…
what is the best practice?
1 build the base inside a blueprint so the whole base is a blueprint, with others blueprints inside like automatic doors and destruction objects etc
2 build the base on the level with everything

other question.
destruction meshes… if I duplicate them that reduces the number of calls, it makes a difference if they are all duplicated in a blueprint or if is duplicated on the level?

thanks in advance