~snip
It doesn't really matter
Well, in the 19th century (before the Civil War) US banks had been issuing gold receipts (or how they were called), and this wasn't a problem as long as they didn't abuse their power, i.e. didn't issue more receipts than they had physical gold in their vaults (gold standard on a private level)
Obviously, they very soon started to exploit the popularity of these notes (I guess the origin of the term banknote refers to that period) by printing receipts not backed up by anything which led to bank runs and bankruptcies (probably another term originating in those times), but that's a different story
Presumably, if the same situation would ever happen to "Paper Bitcoin" eventually. It would just tatter the credibility of Bitcoin, thus making it harder for adaptation.
Worst case, the government will be forced to take action.
~snip
I don't really know. But who could say some 20+ years ago that Bitcoin itself was possible (I refer to its decentralized nature mostly)? The thing is, if you can check the authenticity of a paper bitcoin, i.e. to check that it hasn't been spent by someone else, it's okay. In fact, there are OpenDime devices which serve as physical bitcoins, so we can actually say that there is a way to check that in a "provably fair" manner
True, no one could've said it.
Yes, there is (I almost forgot about that). But that doesn't seem to be genuinely "physical" as you still need to access a wallet (storage) for that. But nevertheless, yes, it could be one way to check authenticity or rather it could be the only way to check authenticity.
~snip
We don't need to, but technically, there will certainly be certain discrepancies - either premiums or discounts - depending on the ease of use and such things
I would prefer, it should be accessible via smartphone (or something), e.g. scanning QR codes, but this time a device, let's say from a store, will scan your (temporary: address) code that will automatically transact a payment. Isn't that more reliable and convenient? Also, we don't have to worry about the smartphone in the case of being stolen as the wallet (storage) isn't really the smartphone.