I’m a bit obsessed with efficiency
- use blueprints
- be efficient
You get to choose only one. Can’t have both. 
From my experience efficiency is getting something working first - that’s you being efficient. Refactor later - that’s making your code (a wee bit more) efficient. There’s no need to optimise something that is not there.
Also: Testing and Optimizing Your Content | Unreal Engine 5.3 Documentation
I don’t want the game to go smooth but
in a menu there is a drop in fps. It
would be a bit embarrassing.
I’m not sure I follow. Are you saying that this one function has a bigger performance hit than the actual game? Why - are you doing some heavy async lifting while paused?