QuickBooks Commerce does not sync with QuickBooks's Inventory Management feature. Therefore your products in QuickBooks Commerce will not be synced with your products on QuickBooks Online. Changes and updates to products on either end will NOT be reflected on the other.
Furthermore, products must be set with the 'Service' type in QuickBooks. This lets QuickBooks know that the inventory of these items is managed in QuickBooks Commerce. Assigning it as an 'Inventory' will stop the link between the two systems, which then basically makes QuickBooks to manage the stock of these items.