1. Fiat can be created from thin air; cryptocurrencies has a set amount of coins to be mined/acquired.
2. Inflationary (fiat) vs Deflationary (cryptocurrency)
3. Region-restricted purchases (fiat); shopping with no borders (cryptocurrency)
4. Requires an intermediary to store money (fiat); you're your own bank (crypto)
These are some of the things that differ crypto from fiat. There's a lot more aside from those things but that's just what I thought off the top of my head.
2. At this point it is hard to say how bitcoin or other cryptos will scale, we have not entered the phase of deflation as new coins are still being mined.
3. Pretty much I agree with you here, the minor problem is really limited selection of merchants/services accepting BTC payment.
4. Not exactly, you can store your cash on your own, but yes banks are kinda obsolete and harmful entities IMO.