Use of iCloud as a backup facility

I think I already know the answer to this question but I'd like some confirmation.

Situation: I am a photographer and I have acquired a 2021 iPad Pro 11 to do post-production on my photos when I am away from base. My workflow is that I transfer the RAW files from my DSLR via USB to the iPad then upload the ones I want to work on to Lightroom for iPad. This all works fine

My idea was that I would use iCloud as backup for the RAW files I have transferred from my camera. But everything I read on the subject implies that I may use iCloud merely as a synchronization space. It is all or nothing.

Well I do not want all the pictures on my iPad synced to the cloud and I certainly do not want thousands of MBytes synced down to my iPhone which has minimal local storage.

So therefore I must abstain from connecting Photos on the iPhone to iCloud as I cannot pick which photos I would want synced back to the phone? But i might have liked to use the phone to browse what was on the cloud storage but I can't because it will insist on syncing down to the phone and I will run out of storage.

Is this right? is this really how it works? In which case it is of no practical use to me and I might as well stick with my free 5 GB quota of storage. I can understand the commercial motives Apple may have here. I guess if you're part of the Apple hive mind on how data ought to be organised then it is fine and dandy. But it is frustrating when you want to do a simple thing that other cloud storages permit you to do.

I guess I know what I have to do.