I recommend installing the free demo version ahead of buying and check the necessity for session management. The OC Session Manager module is mostly meant for OpenCart 3. Opencart stores some consumer details (language, currency, cart, and many others.) in PHP classes. OpenCart can store this data in two strategies: https://danteuogxp.verybigblog.com/31261270/create-your-own-ecommerce-with-opencart-an-overview