What do I think:
Moore is a TE in the making, neither the top speed nor the vertical that Massington or Seals-Jones has. A long strider as you can see in his video but uses his body well (is a very good power forward for Clarksville). Basically can post up as well as any receiver in Texas HS including Seals-Jones. Likes the ball away from his body so he can go get it however focus seems to be hit & miss on him. Incredible athlete and in the right role would be a tremendous get.
Massington is all that and more. Top end speed rivals many of the 5-10 guys but doesn't get there as quick as many would like. Likes the deep ball and plays with strength and a desire to get to the ball. Massington, depending upon the results of his rehab can be in an elite receiver category.
Seals-Jones another possible TE in the making but with great strength, hands and very good quickness. Has great strength but not always willing to use it, but so often in a mismatch situation hard to tell his true desire. An elite ball receiver already and likes to play above the defenders, doesn't wait for the ball but attacks it.
All 3 are not the sharpest route runners, but Massington seems to be crisper.