iCloud and Apple Photos Confusion

I am confused.

My school started with Google Photos which I use and understand. I like[d] Google Photos for its ability to clean your phone and keep photos backed up. We are now trying an all-in-one solution with Apple using their iCloud service. 

And this is where the confusion starts. 

I like Apple devices, but I have always found [most of] their software to be confusing and convoluted.  Instead, my preferred option has been to pair Google software with Apple products.

Reading this [old] article that was recommended reading from the Apple Support forums, it seems that you should opt to keep the original photos on your Mac and optimized photos on your iPhone/iPad since it probably has less storage.

In most cases, optimized is what you want:

• In iOS, go to Settings > iCloud > Photos and tap Optimize iPhone (or iPad) Storage.
• In macOS, switch to Photos and select Photos > iCloud, and select Optimize Mac Storage.