I've saved several files and photos onto my MacBook. I've had iCloud syncing on my iPhone. I have synced my iPhone's media using the Photos app on my MacBook. I don't think I've ever synced my MacBook with iCloud.
I'd like to save things onto my Mac (or external hard drives) permanently, with iCloud as a tertiary backup for my phone. I've heard some horror stories from coworkers where they synced their MacBook with iCloud and rather than just add the files from iCloud, it deleted everything on the MacBook and then added the iCloud files.
Obviously I could take a slower route, like using Air Drop, emailing the pictures, or using a different cloud storage service to transfer, but if I could it to work without deleting stuff, I'd like to use iCloud. How do I avoid losing my non-iCloud files while also syncing the iCloud files?