Would the timing be similar if you used whole on-the bone chicken breasts?

Any time you can cook with bone-in is preferred (better flavor) it's usually cheaper per pound as well. The bone does take longer to heat up so make sure the juices run clear and all pink is gone from meat adjacent to the bone, but my best advice is use an instant read thermometer to be absolutely sure the meat is up to temperature.

Probably pretty close, since chicken breasts are generally larger than thighs and drumsticks. Altho dark meat usually takes a bit longer to cook than the light.