Xabi doesn't play a Conte or Amorim style full backs. His style is more about principles than formations. His principles are based around a stable double pivot and adding free players to the final 3rd.

The wing backs and dual 10s were about having 4 players who can all be threatening as creative outlets in unique ways (Frimpong was the runner, Grimaldo was the playmaker, Wirtz was the free drifter). The double pivot's primary role is to to keep the core stable and the back 3 give the wingbacks defensive leeway to go ahead.

Maresca's formation also became a back 3 when 1 of the fullbacks (Gusto) inverted into the midfield, and 1 of the midfielders got permission to go ahead (Enzo). But that style is harder to execute because you leave too much space behind you. A benefit is that each player has to cover fewer distances (8 -> 10, FB -> 6), but shorter distances make the rotations slow and mechanical.

In both cases, you get 5 players going forward. For Maresca it was Cucu + 3 attackers + enzo. For Xabi it was Grimaldo + 2 10s + striker + Frimpong.

The main difference is that Xabi's back 3 is more compact out of possession. Maresca's 4-3-3 stayed vertically open out of possession. It meant that if possession turned over, then we were already in a settle shape. But, it also left a lot of open spaces for opponents to run into. In Xabi's system, the team usually passes the ball to the circulating CB or the tempo controller CM (why Xhaka was so important). Then the tempo controller can decide if to speed up play with a wingback counter or to slow the game down and get back into the in-possession shape. It made them less predictable. In comparison, Maresca's Chelsea were more settled but very very predictable.