That is a good idea just so that you don’t have to think about any potential privacy issues. Your email could be {firstword}{secondword}{4 numbers} and so long as the words and numbers are randomly generated, you can avoid accidentally including personal references or biases.
Your username does not need to be high-entropy, though. It will be semi-public. So it’s not about strength against dictionary attack or similar, it is just about leaving the selection process up to a random process that isn’t witnessed by a third party. You can write scripts that will generate these kinds of things using Python and the faker library.
Set up a proper backup system for your server. I like to use borg. Just to be safe, make a copy of your drive as well (like full disk rsync). Then do a clean install and restore as if your drive had failed. If your backups missed anything, you will now know and can fix your backup system and can still recover from your rsync’d drive.
You might also want to take this opportunity to start administering your server with code, like using ansible or other remote provisioning tools. This makes your system configuration reproducible so that you only really need to back up a few kinds of data like media files or databases.