[Milhouse]

C recaches all artwork.

Still does not answer my original question:
I am wondering that if after this first run when I start the runs for the other 4 Kodi instances will it run faster or will it take the same amount of time for each instance?

The texture cache of each client is independent of all other clients, so updating the cache on your primary client is going to have no effect on how long it takes to populate the cache on each of your other clients.

However what @redglory is saying is that the "C" option will always re-cache *all* artwork - each time you run this option it will take a very long time, and is definitely not something you want to do (it's debatable if this is ever a good idea - better to just delete Textures13.db/Thumbnails and use the "c" option).

What you should be using is the "c" option (the options are case sensitive!) as this will only cache artwork that is not yet cached. On an empty texture cache it will still take a while to run, but subsequent runs will be much quicker.

The "C" option is really only needed to "fix" already cached artwork that is corrupt or stale, and generally you'd use it only on a specific movie/tvshow/etc., and not the entire library.