I like to recommend installing the free demo version just before paying for and check the necessity for session management. The OC Session Manager module is mainly meant for OpenCart 3. Opencart stores some consumer knowledge (language, currency, cart, and so on.) in PHP sessions. OpenCart can store this info https://spencerpmlbv.boyblogguide.com/31066289/create-your-own-ecommerce-with-opencart-an-overview