4-2-3-1 is also Eriksens best system, but you are right. He is tactically more flexible than Bruno, although I could see Bruno on the wing with Eriksen at 10 in ten Hags system. Eriksen played with fellow dane Lasse Schöne as a double 8 at Ajax and mostly on the left wing in Tottenham, where Delle Ali took the central role. All of this worked out pretty well. I assume you would go with Casemiro at 6 and McT/Eriksen at 8 in our current squad? That is also something I would like to see. If we could get a Kante/FDJ/Höjbjerg/Bentancour type of player instead of McT, it would be an awesome midfield. Where does that leave Bruno, if we do the ETH-Ajax 4-3-3? We don't need a false 9 and is he better than Sancho/Rashford/Anthony on the wing? In games when we need to open up a low standing opposition, I would think so. Anthony and Rashford are players who need space to shine. Bruno created plenty of chances in the midweek game. Against other teams he would sit on the bench though.
By the way. DvB played 8 in an Ajax- midfield anchored by FDJ, and with Lasse Schöne on the other 8 position. Schöne had a lot of Eriksens skills (passing/long range shooting/free kicks), but he was/is a more physical player, able to win tackles. DvB does not do that. Eriksen/DvB would leave an immense workload for Casemiro as the only ball winner in midfield.