Welcome to the Auth0 Community!
Yes, when using the Management API v2 update a user endpoint, you could pass the user_id to update for a specific user.
To allow users to update themselves, you could have a scenario where the user logs in, and you use the access token to find the user’s user_id from the sub claim (whom the token refers to). Then you’ll be able to pass that user_id to the Management API when updating the user.
Hoped this helps!
Please let me know if you have any questions.
Thank you.