interesting, I never considered using iCloud. so you'd just upload home video files to iCloud photos?
Yes, you just keep the photos and videos in the photos app on your Mac, and have them uploaded to iCloud Photos.
Pros of iCloud Photos:
Ease of use.
Upload in the cloud.
Built in to Apple devices.
Memories feature.
Cons of iCloud Photos:
It requires iCloud storage which depending on the amount, it could be expensive over time.
Must keep a back up of your content, if your iCloud loses content and you don't have a back up, Apple won't help you.
Apple devices only, not cross-platform.
Limited features and customization.
No offline viewing.
Plex on the other hand is more than just photos/home movies. It is made for movies, tv shows, music, photos, home movies, music videos, video games, etc. Plex has a lot more customization to really make it your own.
Pros of Plex:
Cross platform, Plex is on everything, iOS, tvOS, MacOS, Windows, Android, Roku, Firestick, etc.
Multiple format videos, music, and photos. Plays almost anything.
Lots of features.
One time payment for life time Plex-pass membership.
Customization on how things are organized and stored.
Free to try.
Off-line viewing in network, or locally stored on devices.
Better UI than Apple's, imo.
Cons of Plex:
More complex set up.
Need a server (might be able to use cloud storage with a server).
Plex Pass for a lot of the features costs a monthly fee if the life time option isn't purchased.
Final suggestion, if you are looking for just a solution for personal photos and videos, iCloud Photos might be a better option for Plex. If the other features of Plex might interest you, then it might be worth trying it.