At the time this thread was started in Feb 2017, I had two touring bikes. On my heavy touring bike I used 55mm or 57mm wide tires. On the lighter bike I used either 40mm wide for predominantly pavement tours or 50mm wide tires for the trips with significant amount of gravel. Both of those bikes were 26 inch wheel bikes.

This thread actually started on Feb 7, 2017 which was the second day of my Florida tour where I was riding with 40mm wide tires, that tour was almost 100 percent pavement. I was quite happy with my tires for that trip, Schwalbe Marathon (with Greenguard).

One month after this thread started, I bought the frame for what became my light touring bike, a titanium frame for a 700c touring bike. I run 37mm wide tires on that, but that bike is pretty much used on tours where I expect mostly or all pavement and ability to resupply often.

I used my light touring bike on my last tour (a month ago), which had some rail trail and towpath gravel, but the 37mm wide tires worked fine on that soil when dry. When saturated with rain, the 37mm wide tires sank in a bit more and slowed me down more than a wider tire would have. That tour was roughly 90 percent pavement, 10 percent rail trail or towpath.

The 37mm or 40mm wide tires clearly give me a rougher ride than the 50mm to 57mm wide tires. And for that reason, I added a suspension seatpost and suspension stem to the light touring bike to soften the ride on 37mm tires before my most recent tour. I was quite happy with that upgrade. [I might start a thread later on my recent suspension upgrade?]

For your pick of 1.75 or 2.00 inch, you are right in the midrange of my personal preferences, based on road type. I like the ability to vary the width for different expected road surface types more than your range which I consider to be pretty narrow. But we pretty much are in agreement on width.