Most cost efficient BP's for level trigger boxes?

I’m testing level streaming with lots of levels where you will always be at the centre of 3x3 levels. Each level has a trigger box which will load and unload other levels.

  1. Is it more cost efficient to have the BP for all triggers in the ‘level blueprint’ or have a separate BP for each trigger box?

  2. This test is having a ‘persistent level’ but I’m not sure this is the best way to go?

Any advice much appreciated.