While there was no style voice display/change options on previous PSR-E series keyboards, I do believe that one of the E473's upgrades is that a style can be revoiced -- however, it cannot be saved back as a style with the new voicing -- you'd just have to saved your newly revoiced style in a registration. But since I believe that revoicing is possible, then seeing what voices are being used for the different style parts should also be possible.
Checking the OTS setting for any Hawaiian style is a great idea -- that can help determine what voices Yamaha believes are "Hawaiian."
And yes, the E473 allows for wide range of editing of sounds such as filter, envelope, reverb, chorusing, and DSP, so that even if a Hawaiian guitar is not directly available, it is likely possible to synthesize it and then save the new sound as a registration.