I just looked and I have 35 companions in my main playthrough, so the cap may be higher than I thought (still no smith though, so they're apparently pretty rare). That post was from a week ago, so things may have changed.
After starting a new campaign real quick I spawned with 21 companions, so it seems there's plenty of cap space for wanderers to be added (If there even is a cap).
As far as the scholar with 0 healing, he is probably an Imperial culture companion. The Aserai one is the one with medicine skill. There's a difference, and if you look at the overview guide I linked you'll see that it matters for a few of the templates as indicated with the culture in parentheses.
I didn't make either of those posts, by the way, I'm just going off of what they discovered.