Saddle bag is popular on the CTC forum but I suspect attaching a suitably large one to many modern saddles may be tricky.
An aluminium rack doesn’t weigh enough to worry about IMO, and you can get racktop bags with side fittings that unzip and collapse out as mini-panniers, which is probably the most versatile option if the racktop bit is big enough.
I’d certainly always have a bar bag for touring, so if you can get away with one of those and a largish saddle bag then that seems the easiest option, though personally I doubt I’d want to tour for more than three or four days with less kit than would require at least one decent-sized rack-mounted bag.
Since when did an all-dayer qualify as touring? That’s just a ride 🙂