I want to officially welcome you to the Community space and I appreciate you for converting into QuickBooks Online. Let me share some information on what to expect once you convert from QuickBooks Desktop to QuickBooks Online
When you switch from QBDT to QBO, there are some things you may notice like transactions are missing, or reports are different and don't match. Moreover, QuickBooks Online doesn't have the same reports as QuickBooks Desktop. This might be the reason why your Accounts Receivable balance doesn't agree with the Customer reports.
Also, the multicurrency may matter why you don't have the same report. Please take note of the following details on how multicurrency once converted:
Transactions with 3 different currency types won’t convert to QuickBooks Online.
Multicurrency preferences will import to QuickBooks Online.
Multicurrency is only available in QuickBooks Online Plus and Advanced.