Adrien was sincerely impressed with Rey.
At first, he didn't really have an opinion of him—just as he didn't have an opinion of anyone else. He had no clue if he could 'use' him, or if he had to be wary of him.
In the end, it turned out the latter was the case.
Their relationship had somewhat evolved and devolved over the months that were spent in H'Trae, but at the moment Adrien was in a rather complicated position when it came to Rey Skylar.
'He's brilliant, and he's outsmarted me in many instances already… almost as though he is a completely different person from the one I am used to.'
Still, anytime he interacted with Rey, something seemed off.
'He seems just like the Rey I had profiled. All those features… his easily-readable expressions, incredible agitation and aversion towards me, and a bunch of other staple things I had associated with him after our interactions.'