I am using the profile2 module and have three different types of registration forms. I am wondering should certain categories be stored in the main profile which is a profile type already constructed by the profile2 module. The fields I was considering putting in main are the name and location of the user and there profile picture. One user profile is for students and another profile is for teachers. I was wondering for the registration form if I should store the name and address details in the main profile and then the more specific details about the student in the student profile and the same format for the teacher profile. I was just wondering which method is more efficient for the drupal database. If I put the location and name in the student profile and the location and name in the teacher profile wouldn't this be duplicates of the fields first and surname and the address. Does this clear things up. I can provide further details if you require them.
I would suggest you have the least amount of profiles required, if you can fit all the fields naturally into the main profile do that. If however you have a large number of fields which warrant another profile, add another for each group of fields which would make sense to bunch together.
For example, if you were building a jobs site... you would have all your account settings for the website in the Account profile like username, email, password. Then create another tab for Education, another for experience etc?
Really it is hard to provide more details on best practice because profiles can have quite a wide scope depending on your specific requirements