Remove user id 1000

You are free to repurpose the default ec2-user account as you wish. If you would like to create a different user ID for the purpose of logging in, you can do so. You'll just need to ensure that the user's home directory is set up and has the appropriate public ssh keys listed in its $HOME/.ssh/authorized-keys file.

In fact, if you run AWS Systems Manager Session Manager on your EC2 instance, you don't need to use ssh to log in at all; you can use Session Manager to log in. Session Manager uses a different user ID for logins (ssm-user, id 1001).