There will be very few USB power supplies that cannot deliver the maximum current demanded by the watch.
Power supply is largely irrelevant to charging time. Expect a bit over 2 hours from zero, less if already partly charged (most new devices will probably be delivered 50-70% charged).
The thing you are referring has not been a thing since ages.
Nickel cadmium batteries was different thing and in those it was good to give long initial charge. Lithium-ion batteries doesn't even need that initial 100% charge, it doesn't matter.
