I’ve used it for years (7 or 8 at least) to sync among my iMac, my MacBookPro, and a Mac mini used as a server (which is always on, so basically everything syncs to it). Since you can set up as many folders as you want for syncing independently I have in the past used it to sync photo projects with friends (who use Windows). I’ve never used it to sync with iOS. The only time I’ve had a problem has been when one of the computer’s clock has gotten off and Resilio Sync refuses to synchronize. Correcting the clock and reconnecting the folder to Resilio Sync fixes the problem. I’ve never lost a file.
I don’t have it but I think if you get the paid version it is capable of syncing files without downloading them to all systems (they call it “Selective Sync”). Perhaps that is what you are looking for with iOS.