Google Duo is essentially Google's answer to FaceTime. It's also one of the most simple video chat apps available. You simply log in, verify your number, and you're good to go. You can video call other Google Duo users like you're making a normal phone call. It also includes a feature called Knock Knock that lets you see what someone is up to before you answer the video call. The app is cross-platform. That means it works between iOS and Android. Rumor is that a web version is coming for computer support eventually. This is about as easy as it gets for video calling apps. It's really very good.
Signal Private Messenger is one of the most popular privacy chat apps. It features end-to-end encryption for all messages, voice calls, and video chats between two Signal users. It focuses a lot on individual chats. There are group chat features, but it's mostly for personal use. This is one of the biggest differences between it and rival privacy chat app Telegram. Video calls worked fine in our testing so we have no trouble recommending them. It's a neat way to get some encrypted chats as well. The app is also completely free and open source. You can't really go wrong with it, but there are better video chat apps if you need group video chats.