I don't really think that Bitcoin in this current state should be used for microtransactions. It's just not convenient to buy a cup of coffee with BTC. One can do that, but it's more convenient to buy it for fiat.
I'm not saying that BTC is useless. I just think that there are better projects out there to be used for microtransactions.
Though Lightning is not quite there yet, there have been great wallets lately. Check out the Phoenix[1] wallet.
As for on-chain, I'm really not sure, but it makes sense for me to accept sort of "coffee transactions" that are worth $2-$4 without waiting for a confirmation, probably with just a minimum of 1 sat/byte fee just to make sure that the transaction actually goes through after a while. Because as far as I know, there's a very low chance that someone would actually risk his/her freedom by attempting a doublespend just to save $2-$4.
[1]
https://phoenix.acinq.co/