What is the best Size/Ratio for Terrain Shadow

Hello Epic Devs.

Sorry I cannot post pictures of the project, but I am looking for ways to deliver great shadow quality to a piece of terrain (Baked Shadows).

What do you recommend would be the perfect size (as big as possible) for amazing shadow quality on lots of trees and foliage that need to be baked.

I am looking for something around what a 512/1024 Resolution would deliver on a piece of Static Mesh if it had foliage on it.

Please let me know, and I am looking for best baked results on the largest size you can.

Currently I have a massive terrain (miles long), next step would be separate the subdivision of the tiles, and split the terrain even further so they are their own smaller terrains, while keeping the shadow quality of the terrain between 2-4, and delivering great shadows.

Thank you in advance, for all the help.