Level streaming solutions

Hi all.
I am trying to find solutions for efficient streaming of areas in an open world game. I know there is stream levels, but is there a way to load specific actors as you come close to them?

Another problem that I faced in level streaming is that it works by adding sub levels to a persistent level. But, level streaming doesn`t stream a sub-level of a sub-level in the persistent level. Is there a way to solve it?

Any help would be greatly appreciated.