I use an iPhone and an iPad.I don’t think you understand the point of iCloud. The whole point of iCloud is sharing the data between all the devices (among other things as if they’re all the same device). It’s Apple’s way, instead of trying to make one device be every format (eg. convertible hybrid laptop tablets).
If you don’t want these devices sharing information then perhaps they should have separate iCloud IDs.
In short, you’re doing it wrong.*
*And no I’m not trying to be a smart ass. I’m genuinely saying your description of what you’re trying to do defies the intention and purpose of iCloud. these items won’t be ”fixed” because they’re not broken.
I want all the photos synced to iCloud on my phone. I turn iCloud backup on.
I don't want them synced to iCloud on my iPad, I turn iCloud backup and photostream off.
If photos are still appearing on the iPad after disabling iCloud backup, photostream is probably turned on.
It's as simple as that!