3 best for me?

[Effendi]

All Italiano MNOs sell prepaid cards at 10€ including 5€ of credit. Sometimes you can get better deals, but that's not the rule.
In Rome 3 should be fine, in Florence not the best, but still ok. Surely TIM, but also Wind, have better coverage, but all 4 operators are ok in big towns.
Wind has no shop at FCO, while at Termini station, or around, you should fine shops for all 4 operators, as far as I know.

And yes, they detect you at once if you do tethering and you pay it.