Access modes
Override hidden if assigned
This is the default mode. Magento's normally visible products remain available. A custom catalog or direct grant can also make an assigned product available to that customer.
Use it when customer assortments should add exceptions without turning the rest of the catalog into a whitelist.
Strict whitelist
Strict mode limits a signed-in customer to products resolved from active assigned catalogs and direct grants. Products outside that set are removed from listings and search, and direct product access uses the configured no-route destination.
Before enabling strict mode, verify at least one complete customer journey: category, search, product page, cart, checkout and My Products. Test a customer with direct catalog assignment and one who receives the catalog through a customer group.
Guests do not have a customer-specific assignment set. Test guest behavior separately instead of assuming it matches a signed-in strict customer.