Re: HSS pickup wiring
If all else is equal, the 250k pots make the humbucker sound warmer. However there is no rule that says humbuckers have to use 500k pots. It really depends on the specifics of the guitar, and how the pickups are designed. Eg. Gibson used 300k control pots for many years. The Fender guitars typically have more treble due to the longer scale length and also tone woods with higher elastic modulus (stiffness). So the 250k controls will often work if the humbuckers are a bit "on the bright side" in Fender strats. In these situations, all is *not* equal, so any 'rule of thumb' may not apply. Its a job for the designer at Fender to choose appropriate pickups that work in combination with the wiring scheme and the character of the instrument.
Obviously its ok to just judge if you like the tone of the Bridge humbucker and single coils, and forget about the specifics of wiring. One other aspect you should think about is the Strat tone in position 2. Sometimes when noiseless pickups and high output humbuckers are combined, you will miss out on getting a traditional quacking-strat tone in the postion 2 "notch position".
Just to complicate matters further, the 2016 American standard Shawbucker strat HSS used a dual gang volume control that combined both 500k and 250k volume control on the one knob. The 500k was wired to the Humbucker, and 250k to the single coils used for neck and middle pickups. In position 2, both 250k and 500k sides of the volume control were switched together in parallel. I am not sure if this still applies to the 2017 professional series.