It’s mostly a matter of how you want to build it. My perception is that speed is a little less important for zone than for the other defenses, and for me, that holds for 3-2 as well as 2-3. The big question revolves around what your 3 gives you (or what you’re looking for in a 3, if you’re set on 3-2 as a base). I like to maintain the flexibility to go back and forth, but if I have a guy I really want to start at the 3 who tends toward speed, his skills will likely be better utilized on the perimeter. If he tends toward rebounding, I’d usually rather have him down low in a 2-3, all else being equal.
I dont personally agree that IQ is less important in preventing fouls in zone; but it is true, I think, that a good zone team will commit fewer fouls, on average. IQ is still part of that, but it’s easier to “cover” for freshmen than in man or press, where they are more easily exploited. If that’s what you mean, then I think you’re right.
Shot blocking is important for bigs in a 3-2, but not quite as important as for the C in a 2-3, and perhaps a little more important than for the forwards in a 2-3. Rebounding is the biggest priority for bigs in a 3-2, in my opinion. A straight zone run well is great for lowering your opponents FG% without fouling. But you need rebounding to take advantage of that, and if you get killed on the boards, it defeats the purpose of making them miss a lot.