Sorry for this, I know you'll not like it, but you have to start from here: https://www.nc700-forum.com/forum/tire-tech-talk/
I had similar questions and what I actually learned is: the tires are (generally) personal preferences and there is no right of wrong.
I trust this guy, FortNine and his "opinion", this is where I also started: YouTube
Since I'm planing to "explore (gravel roads of) Iowa", my plan is to buy Shinko 705. Sadly, they don't last long, so if I don't like them, next time I'm gonna order something else. I would like to buy Heidenau K60 but they are expensive, I can buy 2-3 sets of Shinko.
And, additional note, what I learned from the guys I trust on this forum, "regular" street tires can do some basic off-road/gravel road just fine. In my case it's Michelin PR4.
Hope this can help you anyway...