Reference: https://quickbooks.intuit.com/online/compare/
Customers, Parts and Invoices
Quantum MX Customers, Parts, and Invoice integration features will function normally with all versions of Quickbooks Online.
Inventory
Quantum MX Inventory integration features require Quickbooks Online Plus. Quickbooks Online Simple Start or Essentials products do not support inventory products.
If you are using QBO Simple Start or Essentials, leave the Asset Account setting blank in Quantum MX and all parts will be created in Quickbooks as Non Inventory product items.
If you decide to upgrade to Quickbooks Online Plus in the future, you may enable inventory synchronization features by configuring the COGS Account and Asset Account team settings in Quantum MX. Parts that have been previously pushed to Quickbooks as Non Inventory items may be updated and promoted to Inventory items.
Reference: Converting a Non Inventory Part to Inventory