Would a taller windshield or adjustable deflector make the ride quieter for a tall rider?
Yes but one size doesn't fit all.
I tried multiple aftermarket and home made windshields. None really met my needs. The quietest ones were also the hottest in summer.
I ended up with a Madstad which is adjustable and is the quietest overall that I tried. I like it a lot.
Some helmets are significantly noisier than others. When I made a helmet change from an HJC C12 to a GMax dual sport (which I really like) any remaining buffeting and noise with the Madstad windshield all the way down was much less.
The difference between helmets was also very noticeable on the dual sport, with or without a its windshield.