Davies is better off playing LB in Europe for elite teams because he has more space to attack both with over and under lapping runs. like Theo Hernandez has been doing, like Hakimi, like Bale did at Spurs pre AVB. like TAA has but for different reasons not his dribbling and pace but for his passing from the right channel like Beckham did like Gerrard did before Rafa moved him him to AM/#10 like KDB did/does.
Take Dani Alves probably the greatest attacking FB ever who could dribble/run past his man or pass like a midfield playmaker. When Pep tried to play him him as a RM/RW when he was using 3 at the back in his last season at Barca. He wasn't as effective as he has been from playing in a back 4 in his usual RB position because the space he was use to playing in wasn't there any longer. He went from having 75-80% of the flank to play down to 25-50% of the flank also had defenders closer to him when he received the ball when at RB he had the chance to gather momentum.