It's really close to a 3-2-2-3 in possession due to how high Balde gets and how pronounced Gavi and Pedri are as the inside "forwards" in left and right half-spaces in attack (when Busi and FdJ are the two pivots), in defense it's obviously different. But it's not as pronounced as his Al-Sadd shape because there he used two real wingers, there is more variety with using a fullback in that left winger position because you can easily switch to a back four.
Yes.
Xavi used this system quite early (Benfica game CL), and rediscovered it many times this season (Sociedad away, Inter twice, most importantly Bilbao home), and after RM SuperCopa final it has become the standard for important games
Maybe we could have coped better against Eintracht last season if Xavi was not insistent in the 4-3-3 back then. 3-2-2-3 allows much better penetration IMO.
I personally think it's a problem that out of possession it almost always morphs back into a 4-3-3.
For instance, against Inter we couldn't defend their width, had Xavi stayed with the 3-2-2-3 out of possession as well, we could have had better luck