If you know nothing about password managers to the point where you’re asking a question like this, you should at least start with a cloud based manager.
Also if you use a reputable company, you’re pretty safe. BitWarden is great. LastPass has been absolute bottom of the barrel for years now after LogMeIn bought them.
Ya, my mi band has that, too. It’s called always on display. Since it’s OLED, it doesn’t cause a ton of battery drain, and I can see the time without lifting it.