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I've been using the apidura bar bag for audaxing. Whilst you can't get into it on the move, it is lightweight and can compress down quite nicely leaving space for your hands in all the bar positions.
With the frame bags and saddle bags I've had bad experience with them rubbing the paint quite poorly. I'd hate that to happen to my Isen. So perhaps heli tape might be a solution to the tubes facing the bag if you decide to go for the frame option.
I am seeking a bag that'll take a rain jacket, body warmer and possibly tools and some flip flops or barefoot shoes.
Bar bags all seem to interfere with garmin and lights - my k edge mount has Garmin out front with light underneath.