Re: What are these user accounts doing on my OS?
Those are known as 'service accounts.' They exist for the purpose of running a task under a specific set of permissions or while no real user account is logged in.
You can delete all of them. If Windows needs any of them (like UpdatesUser) it will recreate, but I'm fairly sure MS stopped using those service accounts.
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?