Which Blueprint to use

I’m kind of confused about what to put in what blueprints.
I’ve got a game I’m designing with different levels, blueprints, characters, menus.
So far it’s divided into different projects for testing.
Some things are used for all levels and characters. Some are just for individual characters or levels.
The menu tutorials are all putting the menu in the level BP.

Start Menu: I created a level just for the start screen.
Pause Menu: For all levels except the start screen.

The question is: Why duplicate everything in all of the level blueprints or the character blueprints.
Would the pause menu go into the gameplay BP or would it have to be copied to all levels.

Start Menu is usually contained in its own level, however, the pause menu is usually just an umg widget that pauses the game, invoked with a keypress. The code that invokes it usually lives in the character bp.