Lopetegui. He is a very good coach.
Agreed, he always coached the Spanish youth teams well and the senior NT has noticeably improved since the end of the Del Bosque era. The squad is strong with the young players growing into key roles, the same players that Lopetegui handled during their youth success at the national level. Thiago/Morata/Isco/Koke were part of the team that won the U21 Euros and have all shown to be fairly impressive at the senior level in club football at one time or another. Veterans that won't predictably decline till beyond the World Cup are Pique, Ramos, Busquets, Alba, and maybe Silva/Pedro. Iniesta may bounce back and show that he can still play consistently at his top level. I think Lopetegui has proven that he's capable of being Spain's tournament coach and that they could once more be high level contenders. Better than teams like Holland/Argentina who have key coaching issues to fix before their teams can realistically put up a fight in 2018.
I still think Deulofeu should stay at Milan. Even with the good performance on the right, I strongly believe that LW is the position where he can truly find the form and momentum to realize his potential and deliver his most capable attacking threat. Neymar won't be pushed out so he's stuck on the right. Barca can probably do better in terms of fit for the pursuit of a RW (though the likes of Dembele would admittedly be several times more expensive) and Deulofeu can reach a level of play at a solid team in his best position that he likely wouldn't at Barca. A move to a big club could be in his future, a player of his innate talent can plausibly explode to an elite level under the right conditions.