I would translate this:

Person B: Though, from what you’ve told me, it doesn’t seem like he was much of a rival to you, anyway.

like this:

Personne B: Quoique, d’après ce que vous m’avez dit, il ne semblait pas être un rival important pour vous, de toute façon.

Hope this will help!

The question is about using the past indication on avoir l’air de and present indication on être un rival dangereux, or the contrary.

I prefer the first one (avait l’air d’être) because you don’t know where he is now, so you remember what he looked like in those days you are talking about.

De quoi avait-il l’air, à cette époque ?

Pas d'(être) un rival dangereux, en tout cas.

I’d use the second one if the guy is in front of me now and I can tell by his look that he probably wasn’t a rival in those days. But maybe someone will tell you that nowadays he looks inoffensive, but it wasn’t the case at that time.

De quoi a-t-il l’air, aujourd’hui ?

Pas d’avoir été un rival dangereux, en tout cas.