Repack BSAs for with no compression. It is faster.
To be safe, keep the original BSAs backed up somewhere.
BSAs count toward the soft cap of 300-400 plugins and BSAs.
The original Meshes BSA contains files with leading spaces.
After PyFFI-optimizing the extracted meshes, repack the folder that the optimized meshes are in, directly. Do not move them; otherwise, the name will be altered.
Do not forget to copy over the rest of the original meshes BSA into the "out" folder (choosing "no to all" when prompted to overwrite) if using the "Run PyFFI" method.
There will be duplicates of the un-optimized files that had the leading spaces after the copy because the spaces are removed in the process. The "renamed" files should probably be removed.
The game will crash if the original meshes BSA is repacked without at least all of the original meshes.
Note: TES4Files automatically corrects texture paths with the wrong slashes in the file paths. Unless you are sure that the BSAs file paths are correct, using TES4Files is safer. The original BSAs are fine, of course.