Allow me to share my thoughts on how Making Tax Digital (MTD) works with QuickBooks Online (QBO).
Using the MTD feature in QBO doesn't need you to connect your bank account. You only need to authorise QuickBooks to interact with HMRC, so you can submit your VAT return from within the product.
With that said, you still have to manually pay your VAT to HMRC.
I've listed a couple of articles that'll provide you more details about this feature.