I watched a good amount of Clinton-Dix and I can see why the rumors are that he was signed to play FS. He's really fluid in space and has good range but he's very passive when crashing down to support the run, he is pretty timid when attacking the run and goes low almost every time. He more or less refuses to take on blockers down field and attempts to work around them, although he is surprisingly solid when attacking receivers after the catch.
He seems to not like taking on RB's once they have a head of steam, and I haven't seen him actually engage an OL downfield once in 3 games as he always looks for ways around them.
The upside is that he seems reliable on the back end and rarely gets beaten as the last line of defense. One of the games I watched was KC and he did a good job keeping over the top of Hill on several occasions where Hill completely roasted the CB and had opened up a good 4-5 yards of vertical separation with Clinton-Dix as the single high safety.
He's very aggressive breaking towards the ball once he reads route combinations and sees the QB setting up to throw, which is presumably why he has about as many INT's as our entire secondary combined in the last 5 years.
Long story short, he's a legitimate starting safety with ball skills and range, yet is very unreliable as a tackler in the open field against RB's especially.