I don't see many good ways to mount a rear rack on that frame ,
I Suggest a Bike trailer,
that solves the what bags should I buy question, also .
has a selection,
I would stay away from single wheel type .
as they torque the rear triangle of the bike.
I got one of these http://carryfreedom.com/city.html
It folds flat for transport and the bag is snap buckle removable,
and can be worn like a backpack..
probably go in the OHC .
+ you can load a small duffel bag on top of it , for additional space..
Perhaps the checked Luggage Bag.. brought with.
I'd consider ordering and having it shipped to reserved Hotel or a parcel service store in the Arrival city.
Or they have a Korean Dealer http://www.carryfreedom.co.kr/
to have already and practice riding packing and loading the combination at home.
as far as Gearing goes low ratios are small tooth count gears on the Cranks turning Big sized cogs on the back, Mountain bike cassette, they go from 12 to 34 tooth these days .
Triple crank would offer a low gear up front , But then You have the Left Brifter indexing to deal with, and not all triple front shifters work with road combination brake/shift levers and Klick in the right places.
but a compact double [50/34] offers a 34 tooth low gear cog ,
so that gives you a 1:1 gear .. multiplied by the wheel size ,
functionally like a unicycle gear ..