How does one allow additional family members, guests, and/or renters to operate blinds in the home? Are you able to grant access without allowing the additional users to change the setup?

No, the app does not allow additional users to login to their own Tuiss SmartView account using their own credentials, to control blinds from another Tuiss SmartView account. Alternatively, an optional remote control can be used to conveniently operate Tuiss SmartView blinds for additional family members and/or renters.