Tactics:
I Will not 2-3 ever: The SF/PF have to have extremely high OD for their position for this to work. For example, the SF/PF will typically handle about 25-35% of the total 3 pointers. To think of this zone in terms of traditional thing (which the game does not follow btw, it's a math game), it is basically saying that 3 pointers from the corners will be guarded by the nearest member of the 3 man group. The amount of times your PF has 5+ OD is limited at best, and the times that a u21 big will have 10 OD and have enough skills inside to be useful? even in a big nation, that number is zero in the amount of weeks you have to pull it off. I think i've only had 1 big make it close, and even then they sacrificed rebounding down to 2-3 levels below that of other bigs on the team and Id 1 level below as well. Not to mention that a 2-3 is really only a reasonable play in a situation where you believe doing so will blow your opponent out by 20+ rebounds, with many of those boards being offensive boards, so you ideally want to utilize an inside SF at SF, and two bigs at PF/C.
I Will not 1-3-1 ever: Similar to the issue of not having bigs with 10 OD, the amount of times you have guards with 10 ID is few and far between. And the SG takes considerably more than a man to man setup or most any other setup.
I tend to default to Man and 3-2 defensively: I man to man in games where i think that a traditional lineup will be played by the opponent, and said lineup will play mostly neutral and inside offenses. I tend to go to the 3-2 against teams that i feel are not capable of a proper flow rating and a proper rebounding rating, and against teams that i feel have a chance at playing a patient with a player out of position. The 3-2's shot distribution also leaves fewer scenarios than the other zones that lead to a poor defender matching up with a real offensive weapon. I have also been 50/50 in mind games where the opponent assumes i will default to a 3-2 or a man against them and i play it opposite of their expectations. Unfortunately, has told you, such a thing cost the US a chance at gold in season 39 to some degree (although i contend i had to Playoff Crunch Time to have a realistic shot of an upset).
Why have you turned your back on America's u21 programs?
If you want to know why i don't want to be a part of the u21 USA team, i suggest you take a gander at the spam and the craziness in that u21 thread. Then let a few of those guys run rampant on discord all day long without punishment, and then let them also spam mail onsite with no BB punishment. If i wanted to watch a circus act, given that Ringling Bros. has stopped bringing the circus to town i suppose that would have to suffice for me. But no, i have no aspirations any time soon of participating in the us u21. Maybe if those managers eventually fade away perhaps :). If i turned my back on the u21/nt program entirely, i'd have fired Winston Pham from my team. Seeing as i haven't done that, i haven't turned my back on anyone.