My 16GB iPhone 5S worked fine after 30 mins or so upgrading tp iOS 10. I have over 3,000 photos on there, and all seems ok. There are some new default Albums, but nothing is ever moved out of the main "All Photos" album, so that's ok.
The "Press Home To Unlock" uses the fingerprint reader immediately. If I use a different finger, the passcode screen comes up. None of my security settings were affected as far as I can see.