If a person is sent a link as a sub user, what account do they sign into to see it?

Also, if they have their own account and are given sub user permissions, aren't they still able to create their own forms under their account?

We are asking to try and contain the activity in the forms, but if sub users can still create their own forms on their own accounts we are concerned about certain forms being created/duplicated outside of the main account.

Hello usjaclean,

Yes sub-user account will be able to create forms in their own account.

Please note that if you already have a free account and then someone adds you as a sub-user account, you will be able to view/edit shared form as well as create your own form as well. 

There should not be any concern as even if forms are created in sub-user account, you should only embed form which is created in master account.

Thank you!