Hello !!
For creating efficient always use the largest section component (2x2) which is recommanded. Pleas refer to landscand size reommandation in order to meet your demands.
You can read more on landscape size vs their memory here ;
Landscape Technical Guide | Unreal Engine 4.27 Documentation
If you wonder how to setup your map properly here is a topic I discussed with another fellow which might answers a lot of your questions;
Start level without all region Loaded - Development / World Creation - Epic Developer Community Forums (unrealengine.com)
I explained how to setup your Runtime Grid and other system if you want to use World Composition.