What system suits these players?
I guess it's not a return to a particular system they're shouting about, but a return to certain "norms". Bruno as a free roaming #10 with two midfielders behind him for cover and the rest upfront trying to adjust to him. Same old, same old...
Otherwise, the issues are pretty much the same: You can argue that we don't have WBs to stretch the pitch and provide creativity in the wide areas in the 343, but we don't have wingers to do that in a 4231 either. You can also argue that we don't have the #10s to receive the ball on the half-turn between the lines to make Amorim's system work, but the synergies weren't there under different managers too for the very same reasons. And it goes on and on.
What has changed is the new guy's persistence
not to return to the "norm" because he believes his system will pay dividends in the near future and will be able to take us further than the tried formula.
Anyway, i have faith in him, but he needs to work around some of the problems, at least until next summer. For example, the three "pure" centre-halves plus Ugarte in front of them is overkill. I haven't watched SCP, but my guess would be that, there, at least one of the three was able to step into the midfield during the build-up. It also doesn't mean that Ugarte is a bad player, but... the whole thing is just too much. And it becomes even worse with his WBs of choice. Perhaps, he's seen us under ETH and came here with the though to play it safe at first, make the team more compact, and move forward. But it's not working for him.
And truth be told, when the system depends on the likes of Dalot and Mazraui seeing so much of the ball (especially the former), you're asking for trouble. OK, Rashford is lazy. Try Garnacho on the left wing. Also, Amad playing in the hole is the right idea, but it's coming much too soon. Take some risks, see what happens. Eriksen, though his legs are gone, is the only midfielder you have who has an understanding of what tempo is in football. Things like that.
Right now, he gives out the impression that he doesn't want what happened to Solskjaer and ETH happening to him. But "finding the right balance" at this level of football isn't about steadying the ship. It's about making it work by playing as many good on the ball players as possible. It's not your team, that's fine. But take a risk or two, show me that the intent is there and i'll believe in the system.