I think the jososoft midi2style program is much better than the Yamaha one.
I just installed both of them. No option to revoice, edit voices etc.
Also the style output will be based on the quality of the midi so the better the midi file the better the style output.
Yes you can, click the main edit. More detailed edit can be found by clicking the tab-edit -open detailed edit.
options there to revoice and also change parameters by clicking the track number as it layed out MA + Main A MB= Main B etc.
In each column your can the click on the number assigned say C1 or C2 then it opens up a window to change how you want it to work, chord etc.
Your best bet is to listen to the Midi first so you can then assign a melody line etc by reanylising and tick the box with the melody in then you can adjust the rest.