Zoho creator license

Dear All,
I am new to Zoho and just going through the tutorials to consider developing an app for my own business. I want an app to collect daily reports data from my employees at different remote site locations. So my employees only input data into the forms that I create.
I need the employees to have access control to login using their credentials and have restricted access to the forms based on the login credentials.
Now to do this kind of setup do I need all my employees to be paid users (with subscription fee) of ZoHo creator? OR since they are only entering data can they be just be users of my app that I developed.
If I go with the Professional subscription, I have a customer portal as add-on. In my case our engineers are like my customers. Do each and everyone who sign up in the portal needs to be a paid user of zoho creator. can they have access settings and permissions?
Thank you.