In Family Setup, The following features and apps are not available: Medications, respiratory rate, irregular heart rhythm notifications, ECG, AFib History, Cycle Tracking, Sleep, Wrist Temperature, Blood Oxygen, Walking Steadiness, Audiobooks, Remote, News, Shortcuts, and the double tap gesture.

https://support.apple.com/en-us/HT211768

Since sleep tracking isn’t supported, you’ll probably have to reset it to get the sleep app to show up.

Low power mode, or temperature of the phone will lower screen brightness without ability to override.

It stores as many photos in iCloud as possible based on available iPhone storage. I have around 10 GB of available storage on my device and every pic I take is offloaded almost immediately. My library is only taking up around 500MB on device and 15GB in iCloud.