I have a Dart Marlin screen on mine. It has moved the airflow off my chest and pushed it around the helmet area, it is still reasonably clean air.
I bought the Moto Guzzi rack unseen when I ordered the bike. With hindsight I wish I hadn’t. I bought a Givi top box plate to go on the rack and the rack is too small to safely mount it. So I started a search for a bag to mount to it and have yet been able to find a bag suit. There are probably better options out there.