Frame bags don't appear to be a problem in cross winds. Big bar bags are, I know from experience.
There's no actual evidence that I've seen that apidura type saddle packs are aerodynamic. Rack packs are lower, stick out less, but the rack struts would cause drag. They are more accessible though. Im weighing up luggage options but will most likely use a rack pack.
I'd have thought rack packs being lower actually an aero disadvantage because instead of being behind your arse, they're behind your legs/seatpost which means they would see more air.
Frame bags don't appear to be a problem in cross winds. Big bar bags are, I know from experience.
There's no actual evidence that I've seen that apidura type saddle packs are aerodynamic. Rack packs are lower, stick out less, but the rack struts would cause drag. They are more accessible though. Im weighing up luggage options but will most likely use a rack pack.