Well, some of the randonneurs I know use Compass tires because they're the most wonderful things ever, etc., then you read of their adventures riding a 400k in the rain and having 8 flats in the process or something like that, and it makes you wonder just what they're thinking.
Anyway, my experience- riding Worksman cruiser, using 26x2-1/4" tires that run about $8 each- maybe a flat every 1,000 miles.
Got my Sojourn, it came with Vittoria Randonneur tires 35x700- and very few if any flats.
Switched to Gatorskins, 32mm and 28mm- very few flats.
On my single bike, using Continental 4 seasons- very few flats.
This leads me to believe that wide tires at low pressure don't prevent flats. Having "good" tires, from a flat-proof point of view, does.
Anyway, my advice, use whatever tire you have on there and go ride your 200k, no reason to experiment for that. If you change tires, get in a bunch of local riding before setting off on a 200k, but don't expect it to make a huge difference.
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"be careful this rando stuff is addictive and dan's the 'pusher'."