Thanks for the explaination. That clears things up for me. ( at least for now! ) Great job, I know you've made many people happy with this contribution!
Yes. Inventory is tracked normally in Quickbooks for sales of Inventory items. It doesn't matter if the invoice is paid or not.
If you have inventory turned on in osC, you'll need to set the stock level to match what's in Quickbooks. So, if stock is 50 units in osC and QB, when you make a sale of two pieces and import it with QBI, then both will show 48 pieces. But if the count starts with 40 in osC and 50 in Quickbooks, then you'll end up with 38 and 48. So, the number of units sold stays on track, but you need to make sure that the starting inventory count is the same in both osC and QBI, because QBI does not do any transfer of the total inventory information.
Just to clarify the payments options (I will explain all the options in a future revision of the manual, but a lot of people were clamouring for me to get version 1.00 released, so I didn't get this part explained fully yet).
Import payments with Invoice: If you do credit card sales with an online gateway, like Authorize.net, turn this on. If you do credit card sales, but process the credit card manually later, then turn it off and record your payments in Quickbooks later when you process the card or use the QB Merchant account.
Import CC payments as Sales Receipt: If you use a gateway, check this and any paid CC sales will import as sales receipts instead of invoices and payments. This is better, because you don't have to manually check off which invoice is paid. Note, if you choose this feature, then "Import Payments with Invoice" is over-ridden.
No questions are dumb.