Expanding the range of capabilities of a gravel bike
To me, gravel bikes seem mostly like cross bikes with a bit more money they can take from your wallet. 

1) Road and mountain shifters and derailleurs don't play nice with each other at 11 speed, so this question is moot. If you want to check a particular crankset on the bike, look at the width and the type of BB setup. I don't see why you'd want to switch to a mountain drivetrain in the first place. 

2) If a wheel is 700c, you can technically mount any tire on it thats 700c (though you'll have problems if too narrow or too wide). If you look at the width compatibility chart from Sheldon Brown, you'd want a rim with a smaller width. Since you're upgrading, may as well buy the right width. By running this, you increase the risk of pinch flats/rim damage over a more well matched width.