I've unpacked 4 vanilla BSA files (meshes, textures, sounds, voices) for melting with my data folder files.

Everything was done very carefully, respecting overwriting priority, editing Skyrim.INI, etc....but LODs gone crazy !

Nearby objects and scenery are OK...but those distant ones are totally missing.

What have I done wrong ?

(thanks in advance for any help).
PS.: Not so important but one more question : My data folder reached 30 GB. My load time is Looooooooong ! Anything I can do for shrinking that time ?