There's no indication at all that Troy would be a successful NFL GM. He's got about as stout a resume in that department as Matt Millen did when he took over the Lions. That's not to say he couldn't do it, but it's a risky proposition that is honestly a pipe dream as we know Jerry's not going to bring in anyone for the job.
As to Tony, if he were to abandon the spotlight for coaching, I think his ceiling would be OC. He had serious problems with leadership while he was a QB, so I don't see where he'd somehow do better in that department as a coach. There have been instances of former Cowboys that didn't respect Romo all that much, and little indication he did a lot to earn any respect beyond his general play.
Honestly, lets face it on Romo, he likes the spotlight and he enjoys being performative and being the center of attention. You can tell it in his demeanor and overall charisma. I think he's found his true calling in broadcasting and individual sport like Golf. I can't see him giving that up to be in the often thankless firing line as an NFL coach.