What the numbers on a charger mean

Watts is the number that matters, and it is just volts multiplied by amps. A 5V 3A charger is 15W. A 9V 2A charger is 18W, so it is the faster of the two even though the amps are lower.

Your phone takes only what it is built to take. Plugging a 65W charger into a phone rated for 18W does not hurt it and does not speed it up either.

Buy for the highest-wattage device you own, and everything below it charges fine from the same brick.