What do you mean by WR1? In my opinion if you want to be good at the spread you better not have one WR dominate in catches. They all have to get a lot of touches. Makes it much harder to defend. I am assuming that is what you meant I was just not sure.
Z - great all around
Y - should lead in touches has to be able to blow the top off and run all the quick game. Can be smaller quicker - i think put your best guy here.
H - can be many different body types - I like the slot TE type the best
X - should lead in highest yards per catch - your fastest WR.
This is just my opinion - I have coached the spread over 20 years. I think the spread allows each coach to really emphasize the type of talent he has to work with.