What to do with a local user account when typing into a domain?

Question

Active Directory

Began to study Active Directory.
And I don’t understand something)
1) When you enter a computer into a domain, it will have two accounts, local and domain.
So what's the use of domain account group policies if a user can easily log into a local account with administrator rights and do whatever he wants?! What to do with the built-in account then? Set a password?
2) If the user worked in a local account, had his own location of shortcuts, settings, wallpapers, etc., then when he enters the computer into the domain, he will have a clean desktop. How to transfer all user data and settings to a domain?

UPD:
Advise good books and courses on AD. What I don’t watch, everything is just about how to install ad, create a forest,
add the computer to the domain. And that's all. And then what?
Thank you)

Answer 1

1) Domain policies (computer policy) override the settings made by the local admin. If the computer sniffed at the DC at boot, it pulls policies from it and applies them, after which some of the policies and settings become inaccessible to the local admin (which ones you configure in the domain will be blocked).
2) Copy the local user profile directory to the directory created when the domain user logged in, remembering to set permissions and ownership.
UPD: And then life, which is so different for each domain, that you can’t push it into a book. DCs act as a credential storage center and a single point of trust for the entire domain, and why you need a domain varies from "test" to "deploy an authentication system for the whole world" aka Azure.

Answer 2

Local entries must be deleted when entering the domain.
For built-in local Administrator there is LAPS
https://www.microsoft.com/en-us/download/details.a...