Advise Recommended Navmesh Bounds Volume Size

I’m wondering what are the implications of having extremely large navmesh bounds volume ( 100/150m x 100/150m) vs many small pieces ( 30-50m x 30-50m )
is one always better than the other? Obviously having smaller piece requires more level design work and can accurately wrap around the level, making less wastage, but are there overheads for these?

what are the common best practice and general advise surrounding this in terms of rebuilding performance. we’re using dynamic navmesh and is hoping we could take steps to improve the performance of regenerating.