Are any of the rando bags really that waterproof though... they all have stitched seams and huge top opening... I suppose you could go all out and have a floating welded roll-top inner, but that'd add weight, cost and compromise ease of access.
With any bike-luggage solution you should always be stashing stuff in dry bags if you don't want it getting wet, whatever the manufacturer claims.
Even then, I'd still pop anything vital in a proper dry bag as they'll hold any water you might accidentally introduce (grabbing that last tube, mid downpour with soggy sleeves gloves/sleeves... that sneaky beer you're saving for later that ends up punctured by a stray tent peg...)
Are any of the rando bags really that waterproof though... they all have stitched seams and huge top opening... I suppose you could go all out and have a floating welded roll-top inner, but that'd add weight, cost and compromise ease of access.
With any bike-luggage solution you should always be stashing stuff in dry bags if you don't want it getting wet, whatever the manufacturer claims.