Editing or deleting a profile is easy.
You can either do this from the Profile Selection when you load up FitXR, or from within the Settings of the app.
From the Profile Selector
When loading up the FitXR app, you'll first be met with this screen to choose which Profile you'd like to load. To edit or delete one of the profiles, all you have to do is click the "Manage Profiles" button at the bottom of the screen - and then click whichever profile you'd like to change.
This will then pull up an editor window, through which you can change the name, email address, image, or simply delete the account if you want to.
From Settings
If you're already loaded into a Profile, you can edit or delete it from within Settings.
The image above shows the Profile Settings for Quest - which will show you the Meta Avatar editor on the left hand side. In Pico, you won't be shown that editor.
From this screen you can change the name, email, language, and image for the profile - and next to the "Switch Profiles" button you'll find a trashcan icon that will allow you to delete the profile if desired.