You could start here https://http-download.intuit.com/http.intuit/CMO/accountants/tax/2021/lacerte/documents/2021_LACERTE...

REP is the fee charged for extra returns outside the firm license, e.g. new state, 706, ...

There is also a charge for "seats" - i.e. workstations. One office with two workstations that 6 people share is charged for 2 workstations. 

Pay per return is here https://proconnect.intuit.com/lacerte/pricing-details/

Compare products : https://proconnect.intuit.com/community/form-1040/help/comparing-lacerte-and-proseries-and-proconnec...

Each has their own unique "look" and input style.