Infuse will currently sync corrections made in a library to iCloud, but everything else remains on each device. This means that every device is required to re-fetch all the metadata and library matching. This approach is fine for small libraries, but it's inefficient, time-consuming, and borderline impossible for large libraries.
In order for my Apple TV to index everything, it took two days of leaving it on and not watching anything, because Infuse stops fetching while streaming. In that time, I was also API banned from Google Drive for 16 hours, as my entire library is located on that service; it should be noted that when API banned, Google Drive does not let you stream anything out of it, either, so I wasn't allowed to watch anything during that time. Obviously, this is a huge deterrent in reproducing my libraries elsewhere. I simply won't do it, because I don't want to get API banned again, which I absolutely will. Multiply this by all my devices, and it's clear this is not the best approach. I also just don't want to have to keep every device open and effectively rendering them unusable during that indexing period.
I really want the ability to configure Infuse to upload the entirety of my Infuse library index and metadata to iCloud. I get the reason for only syncing corrections to iCloud right now, but there really should be an option to allow everything to sync up to iCloud for those of us who don't want to waste hours or days waiting to reproduce our large collections. Personally, a few GBs in iCloud is nothing. I would gladly pay the $1.29/mo to Apple's iCloud subscription (if I had no space left) for 50GB of storage if it meant that all my Infuse libraries, indexes, and metadata were saved. Provide a warning in the settings, so people can't accidentally enable it without knowing what they're doing, and voilà. This would mean that all of the work of getting Infuse to a usable state could be reproduced on multiple devices with very little effort, and, most importantly, very little time. I don't see any other way for Infuse to be able to scale with larger libraries.
I say everything should be synced. This means that when iCloud downloads the dump to a new device, that device will show all the libraries and all their metadata--without need to scan the underlying directory structure. If a file has been deleted since the dump, then it can be marked as unavailable. Plex handles it similarly, and the only way to remove dead files is to hit the "Empty Trash" option. We can then choose to run a new scan, but it shouldn't auto-delete these files, and only add new ones.