If you don't have any stray light nearby I would not use a shroud. It helps remove the boundary layer of air on the mirror if no shroud. Also less prone to being affected by wind.
But mainly it assists in keeping the mirror temperature close to ambient.
In terms of the original question, yes a shroud can act as a sail in conditions when wind is present. Condensation is a different issue, and in my experience, it is more likely when there is no wind (depending on temperature and humidity).
Newbie here... I have a 10" collapsible Dob and I can attest to the extra wind shudder when using a shroud.
I've never been affected much by dew on the primary, and installed a small 5v fan which keeps the air circulating now... And can be powered by usb.
