I tried this for a very short time. At first the update didn’t work, until I put it on the charger. But after all update, there is a problem besides the loading time from iCloud. I used to use Microsoft One Drive to backup the photos on iPad, after the switch, most recent photos are all going to lower resolution, which is not expected, and seems that is not reversible. I am not sure how Microsoft is going to fix this link between Apple.
How to save storage space on an iPhone without deleting photos, with iCloud Photo Library.