A. It depends on what GGG wants to do. Acosta and Lletget (or Roldan) don't really solve the problem of verticality if they're playing on the wings. All those guys are going to pinch in and keep possession (which is what Gio would do as well). That's a viable option, but it's a tradeoff that GGG seems to have some reluctance to make. Similarly, even in the 3-3-3-1 that I'm looking at, I'm not sure I wouldn't put Acosta in for Aaronson if I wanted to maximize ball winning and the press. But that's a big creativity trade-off. I look at the depth issue another way. I trust Sands (in the right circumstances) and I trust Acosta and Lletget as well (assuming we have someone else on set pieces). Of the 11 I posted and the ones you've brought up, I'd say that I'm most iffy on Jedi, but I think we're in a situation where I'm pretty comfortable with most of the roster starting most of the qualifiers. There's not a Bornstein.
B. All of these guys are going to play and probably start at least one of the games (except maybe not Sands if we stay 4-3-3 for all three games).
I'm as guilty as anyone of daydreaming what our "Best XI" is, but in reality that stuff is all contextual. There is no Best XI. Even if we were able to assume perfect health, a lack of fatigue, and the top form for each player, matchups would still dictate what a best XI would look like. We might play a back three only against Canada, for instance, because we want our wingbacks to push back their wingbacks instead of letting Davies and Buchanon sit high with an invitation to run at our fullbacks.
Now, I think there's a limit to that. I don't think you can just chop together formations and tactics completely out of the blue to match an opponent. But it makes sense to have at least two "systems," even if one of them (the back three) is more situational. And that's what GGG seems to have.