Love the fact that I do not have to remember more than one password. Actually that’s a lie, have two password I need to remember. Because our government login system is really trying the stupid approach of denying auto-completion by using multiple inputs to screw with password managers.
That’s a another topic you could cover auto-completion for websites fields 
Prior to switching to password manager I had to remember somewhat 20+ passwords which kept becoming harder so you start to create your own mini password manager with insufficient protection.
Then I took the plunge and started using LastPass, it was time consuming going through all those websites and changing password for what was 50+ sites which has been steadily growing ever since.
My vault has well over 150+ passwords, stores my address, credit, SSN, auto fill completion.
Using pass phrases with +22 characters for master password is a bliss while having toopher’s push notification as two step verification.
Lastpass password generator has quick settings for length, lower, upper, special, minimum number. Which I hope most other password managers have too.
Logging in to anything is a breeze. Auto logout after idle for x minutes depending on the device is wonderful.
What really pains me is when website submits limitation when they are storing password, if it is really so hard then simply don’t as you suggested using OAuth2.
It boggles my mind that my bank has agreed to the government login system with a limit of 16 charters of lower cased a-zæøå and 0-91
Using two step verification should be on every important site sadly the bank also allows that to be a piece of cardboard paper.