You can always spawn 2000 of some actors, and change some variable in them from false to true.
First time with cast.
Then dispatcher that they hook to.
And your way of tags
etc.
See for yourself which is fastest.
I had similar problem some years ago:
use blueprint AI or blackboard AI,
so i spawned 500 simple AI bots.
And then i found out it does not matter, most time in big groups is lost on collision detection.
So whole problem with casts may be unimportant.