I have no idea whatsoever about him.
The reality is nobody does. Not scouts, executives, GM's, agents, coaches - maybe not even Kyler himself.
The whole Kyler Murray phenomenon is entirely unprecedented in terms of combining the relevant factors in play: His stature, his projected draft value, his skillset, the baseball option, and potential success at the next level. He has no comparison.
If he's drafted in the top 25 picks - much less the top 10 - the bottom line is some team is either going to look extremely smart, or extremely stupid. There's no middle ground here. Which is
exactly the type of game a team like the Dolphins need to be playing. The only thing worse than being no good for any professional sports organization is being irrelevant. That's what the Dolphins are and have been for 2 decades.
Bottom line is this - don't listen to other people or read other people's opinions on the internet that have no more of a clue about him than you do.
Watch him play. If the size is what concerns you, then go try to find instances on film of where his size was an issue. If any traits concern you, then go find on film where they were an issue.
The only question that you can't find an answer to is the baseball factor. That's the one that concerns me. Other than that, you pretty much touched one of the most important things in your post. He is athletically gifted. However, he's also a legitimately talented passer of the football. This isn't Lamar Jackson or Kordell Stewart out there trying to play quarterback. Murray is a different level as a passer. He's just short.
However, there are valid concerns also. He's got some groupies out there that have never given a balanced assessment in terms of what he does wrong or need to improve on. But the question for NFL teams boils down to this - is he worth the gamble where you're picking? Whether it's #1 overall or #31 overall. That's the question every team will have to ask themselves.
At #13 overall for the Dolphins - he probably is in my opinion.