Photo Library backup, My Photo Stream and OS X Photos app redundancy?

I cannot back up my iPhone 6 Plus because the Photo Library portion of the backup is 6.6 GB, which would exceed my storage limit.

I use My Photo Stream and Photos for OS X, and it seems that all the photos I take are being added automatically to my Photos album on the Mac. I do not use iCloud Photo Library.

My understanding is that the Photo Library contains:

1. My Camera Roll photos, which are already being synced to the Photos album on the Mac in full original resolution, correct?

2. My Camera Roll video clips, which have to be manually imported to Photos by tethering to the Mac, and

3. Shared photo albums, which are already synced on the Photos album on the Mac as well.

Hence, the only things not already backed up/synced automatically in my situation are video clips that I take with the phone, is that correct?

If that is the case, then turning off Photo Library backup in iCloud for my iPhone 6 Plus should only risk losing the video clips taken with my phone which have not already been synced with the Mac?