FaceTime can support up to 32 callers at once, which is a lot to handle on an iPhone screen. If you want a bigger screen you can always use your Mac or iPad. Here's how to make FaceTime calls from your Mac:
The Shortcuts app for iOS lets you program a several step routine that uses multiple apps into a "shortcut" that requires just a tap or two. For instance, you could use the pre-written shortcut Home ETA to send your ETA to your significant other when you are on your way home, reducing to a single tap a process that would normally take finding your ETA with Maps, then composing a text message.
It's pretty commonplace that people share their Netflix accounts with family, friends, roommates, etc., so Netflix lets you have up to five profiles so everybody can have their own playlists, viewing history and suggested titles. But anybody can go into your profile and see what you've been watching and mess up your suggestions by watching things you wouldn't ordinarily watch.
A lot of people like to (or at least used to like to, before they started using smart phones as alarm clocks instead of good old clock radios) wake up to a local news station to hear traffic, weather, sports scores and more, or to their favorite music station. Since your iPhone is capable of tuning into just about any radio station you'd think there would be an option to have the alarm automatically tune to one of your choice.
The data stored on your iPhone is a valuable commodity to both businesses and governments, and if you don't maintain constant vigilance to protect it, it can leak out in any number of ways, including through unscrupulous apps. Aside from tracking your location and purchasing habits among other metrics, apps can also use your iPhone's microphone and camera, potentially allowing them to invade your privacy in the worst possible way - by listening to and watching you. Obviously you want some apps to have access, but there are plenty that don't need it yet ask for it anyway.