I have a technical question on how SegWit works:

With current transactions, the number of confirmations acts as a guarantee of the Bitcoins deposited. Many services require between 3-6 confirmations to show that funds have been deposited.

With SegWit, does this logic still remain?

I may be confused with what SegWit and Lightning does. I've heard some mention that it can give an instantaneous guarantee of fund transfer, however I don't see how this would work without confirmations of the original transaction...