They should work well together.
T-Mac: big, sideline-operating, go-up-and-get it player who threatens vertically by creating big windows at the catch point along the sideline.
XL: freak athlete, designed touch, YAC and tackle-breaking on short/intermediate routes over the middle.
XL looks like a traditional X but has the skill set of a Z: he’s not super refined but almost nobody his size moves as well as he does. He seems overqualified for his role, but that’s a good thing. The offense can generate different types of big plays now.