I see Gylfi more as a number 8 to be honest.
He has scored more goals from outside the box than any current PL player since 2012. So, playing deeper won't curtail this goal threat and allows him to be more of a playmaker - for which he is naturally gifted.
That was one unbelievable strike! I thought it was going way over, but it looped down at speed into the net. Stunning!