FWIW my phone is Android ( Google Nexus 5 )
I did my Ipad 4 and my wifes Iphone 5 Respectively the oldest devices that can do IOS10. Everything worked afterwards. Just like W10 updates I did an extra reboot to be sure!
Because our idevices are old there are practically no visible changes. Supposedly on say, an Ipad Air 2 or an iphone 6, the difference is quite noticeable