Re: mtc vs. double turn
MTC = more tactical click. MTC is simply an available option on some brands of windage and elevation turrets. It has nothing to do with how many turns are available on a turret.
Should you get MTC? Don't know. Some guys like 'em, some don't. The big criticism with them is that the heavy CLUNK at 1.0 mil, 2.0 mil, 3.0 mil, etc, makes it hard to feel the softer CLICK at 1.1 mil, 2.1 mil, 3.1 mil, etc.
How many turns should you get? Again, a personal preference. I'm a fan of at least two turns because it allows the spacing between clicks to be larger. This makes each click more distinguishable, and easier to feel. I think around 9-10 mils per turn is about the perfect spacing. Not too close together, yet enough elevation to handle most shooting distances.