iCloud photos not syncing well with iPhone and iPad, in recognising things like People/Pets

I recently moved from Android to the Apple eco-system and have encountered weird issues.

I have 4K+ photos and videos in Google Photos(90 GB+), and unlike Google Photos, I can't keep photos and videos only on iCloud; they use device space, too. Can this be solved?

So, I have an iPad and iPhone too along with a Mac. I downloaded the photos from Google to iPad and then synced them to iCloud Photos. This way I can access photos on my iPhone too, but features like people/pet recognition only work on iPad, not on iPhone.

How to solve this issue.

What is the sense of iCloud if I still have my device storage used?

Google Photos was far better in this case. Also, AI features like people recognition should not depend on device storage from where actual photos/videos were saved. It should work on cloud storage.

When I downloaded photos on my iPhone, it correctly created featured photos with recognition of people.

I have an iPad with 256 GB and an iPhone with 128 GB. I don't want all storage to be used in my iPhone for older photos only.

I'm thinking of downloading all the google photos on my iPad and then syncing them with iCloud so that my iPhone doesn't have blocked storage. But all the features of iCloud Photos should work on iPhones as well.

Can this be done?