I think you'll find this post useful: Steps of printing barcode and auto fill the for by scanning barcode and continue updating another form - #9 by LN
In that sample form, I used extra questions to ask for confirmation. You could instead use dynamic defaults to set values at the time of QR code scan and allow the user to override them.
That example is also linked to from the documentation (see the bottom of that section). You may also be interested in some of the approaches that use a barcode in the field but keep related information in a CSV form attachment.