Creating Blueprints or using LevelBlueprint

Hello, I am pretty new at UE4 but far enough that ive learned the basics of blueprints, and have created blueprints of obsticals I place around a map (a falling plattform got its own blue print so i just place it in the map and it works), but ive been wondering if i am building a bad habbit, cause, to be honest, i dont realy know what the “level Blueprint” is realy for, if thats where i should create my blueprints that affects the actors in the level, or if its for other stuff, i am basicly kinda worried that one blueprint for stuff that works as a “Prefab” in Unity is more costly in resources (making the game slower).

I might be alittle unclear, so if it is il try to be more precise, but am i doing it wrong.