How to manage multiple users?

Hello to everyone.

Right now I’m thinking to start to use chromeos flex but my main concern is that I have multiple Google accounts (personal, work, etc…).
Can i use them at the same time for different things (like one for chrome, one for docs and one for YouTube) or do i need to switch between them?
When I turn on my pc do I need to put everytime password for my account or can i use simply a code?
I’m sorry if my questions are not clear but english is not my main language.
Thanks for reading