Use email as login

You can activate email login in Settings > Site Users > User Types > Customer > Profile Settings > Predefined Fields:

Login Details
Field Type () Alphanumeric Characters (x) Contact Email Address

To change login for old users please run a SQL query:

update va_users set login=email

Otherwise old users (registered before this change) could still use their old login details. It works this way because email field may not be required during registration so these users need to have a way to login.

After these changes, would ViArt now use the field "login" to populate the field "email" in the order profile?

Yes, it would.

Would this mean that I can remove "Email" from the "show" and "required"

Yes, you can remove it.