I see his ceiling as Dez, Alshon his floor. Both worthy of a 6th pick IMO. Even somewhere in the middle of them would make a great #1. Agreed he's not on Julio's level. I don't think anyone is when you talk about pure all around dominance.
Being only 20 he has plenty of time to sharpen his route running. When he does he can be a force. Hard to jam him at the line, great hands, feet and frame, will win contested balls - so separation is not a huge concern for me. Having a receiver who can just pluck the ball & use their size & strength for YAC would be great to have.
Elliot is a beast and would make a huge impact on any team, I just don't value the position as much as WR. They're more reliant at their main job with the OL infront of them, which fluctuates annually. As where we have the steady constant Joe, combined with a #1 would maximize all opportunities, regardless of how the game dictates or personnel along the OL. WR's have longer life spans as well.
I would rather have Ramsey, Jack, Tunsil or Bosa over Treadwell. Wouldn't complain with Buckner but it's close for me.