If you're only going to be sleeping at hotels and eating at restaurants, I wouldn't worry about bringing panniers and the appropriate rack. You'll need to acquire roomy bags, just for your clothes, repair kit, etc., but nothing that'd max out a decent handlebar bag and trunk bag.

As for whether to do a seatpost rack or a saddle bag, that's a coin toss. I like saddle bags better, but you'd need to either have a saddle with bag loops, or acquire some aftermarket bag loops that clamp to your saddle rails. In my experience wide loads are easier to manage with a saddle bag, but you'll get less rocking when you're out of the saddle with a seatpost-mounted rack.

Is that a carbon seatpost? I would be nervous clamping down a rack onto that thing. No science to back me up there, but something to think about.