Hi there, @SDM2.

You can choose either of the two connection options. If you've set-up Web-connect already as your connection in your bank online banking website and you want to to switch to Express Web-connect. You'll have to disconnect your bank in QuickBooks Online first to refresh the connection, once your done changing your connection type, reconnect again your bank in QuickBooks.

Here's how to disconnect your Bank in QBO:

1. Go to the Banking menu, click on the bank you need to refresh for the connection.
2. Select the Pencil or Edit icon, and choose Edit account info.
3. Tick the Box that states, "Disconnect this account on save."
4. Confirm by clicking the Save and close button.

I added screenshots too.

No worries about your data linked in your QuickBooks because you can always reconnect it, when adding the bank account again just click the + Link account button. Then, choose the account you've used in QuickBooks before you disconnect it. Here's some screenshots for additional information:

For future reference, you can check out this article to help you match and reconcile your bank transactions in QuickBooks Online.

Please don't hesitate to comment below if you need anything. I'll be here to help. Take care.