Obviously 'wing-backs' can essentially be converted full-backs or converted wide midfielders/forwards and if they are the former they might have a defensive mindset/skillset or a more offensive one. There are plenty of full-backs who you can easily imagine being effective attacking wing-backs (someone like Leighton Baines for example) but there are others who would basically revert to being a defender.
So, obviously, I think, it is absolutely critical who the player is as to what kind of wing-back play you might get out of them.
But I think an additional issue is whether or not a player is USED to playing as a wing-back. Taking the England team as an example - Shaw and Trippier are both reasonably effective going forwards but playing as a wing-back is not their natural/familiar role (actually I am not sure about Trippier). It's inevitable, therefore, that they will tend to revert to being more defensive with their positioning etc. England might well have done better when playing 3-5-2 using two wing-backs who were used to the formation.
With this in mind the key must be either to recruit players who are already playing as a wing-back elsewhere (difficult because as I have pointed out before, most teams do not play that way) or to give converted players enough time to learn the role and unlearn their previous one (but they would also need certain attributes to be successful) or to bring through young players who have been schooled through the youth set-up to play in the position.
Sorry - I've been rambling here and have contributed to the thread going off topic.