[tryfos79]

1) I initially set up no. of fanart to be downloaded to 5. It indeed downloaded 5 fanart to my drive. After I changed the no. to 10 and hit -add missing artwork it never downloaded 5 more. I also tried reloading the movie from the info box, the same. I removed the movie from the library, shutdown Kodi, re added, re scanned  it-the same. Only when I removed the movie from the library, deleted all local artwork and rescanned did it add 10 fanart. Is this normal behavior?

Yes, this is normal. Artwork Beef doesn't know which fanart you have so won't download more if any exist locally.
 

2) I can see the movie set poster in the library, but it has not been downloaded to my drive next to the movie file. All relative options regarding downloading movie set fanart in the advanced settings have been checked. This is just a test movie from a set in its folder. I don't have any other movies from the set or a set folder. Where is this file and how can I also download it to the server location next to the movie file?

See the Artwork Beef documentation on file locations for movie set artwork.

3) Is the "preload to cache" setting recommended in such a setup, or will it make the cache huge quickly?

I suggest it if you've got room on your client's primary storage. The image cache is pretty much always the biggest thing consuming local client space, though. I guess a quick and dirty line might be: 4GB no, 8GB possibly if your library isn't real large or you only configure a couple of artwork types, 16GB should cover a large library with many artwork types but not huge, 32GB would take a massive library with all of the artwork to fill.
 

4) How can we download more than just 1 fanart for the types that don't have a slider next to them (for example 2 banners or 2 clearlogos)?
Thanks in advance!

Artwork Beef can be configured to allow you to do this manually only.


@Karellen If you can reproduce this, can you reset the movie to scraped without AB, enable the setting Disable/Enable Artwork Beef debug context items (per skin) and select "AB: Log debug info" on the affected movie, then post the results from the debug log?

Thanks a lot for the detailed answer! Regarding no 2,I had read the documentation, but it only says where the artwork is being pulled from, not where it gets downloaded to, if the relevant download options for movie sets are configured in AB. Kodi has the option to 'show movie sets'even though only one movie is present at the library. Supposing I only have 1 movie of a set in my library (without a parent directory for the set), where does the set's artwork get downloaded to?it's visible in the library but not downloaded to the location. In other words,in order to have a set's collection's artwork downloaded,do we have to have at the source a parent directory (movie collection name) with all movies of the set in their own subfolders?