Hi Graham,
a) If you want just to adjuts or alter any of the 4 OTS voices(any of R1+R2+R3+left)
You choose the voices for eacg OTS e.g OTS1 you presss the Memory button,then the OTS1 button and save the style.
You do the same with all 4 OTS.
You don't have to enter the style creator at all for changing the OTS voices.
b) If you want to change the voices in the style parts(not the OTS voices) or to change anything else in the style, you select the Style Creator (and also call the Mixing Console and make other adjustments also) and save the style.
If it is a preset style you save it as a new style to the user memory or USB.
These two task are different and independent one from another.
We usually use both tasks(we change the OTS voices and also the style parts/voices etc to be suitable for a specific song we want to play).