In the episode when Koga first appears, his wolves attack a human village and kill Rin. Were those regular wolves or full demons like Ginta and Hakkaku, and simply preferred their wolf form?
In my opinion they were regular wolves.
Firstly, because they look like regular wolves. Since, Koga never transformed, I cannot be sure about what a wolf demon's transformation would look like. But taking the example of Sesshomaru, Inu no Taisho and even Naraku, we can say that a demon's transformation looks much different from the actual form of the being. I mean, they definitely don't look like a normal dog or a normal spider. So, a wolf demon probably couldn't transform into such a normal looking wolf. This point counters the argument that they were wolf demons transformed into their wolf form.
Secondly, as far as I can recall, there have not been any appearances of demons that look like normal beings. Here I do not include the demons that were in disguise. The weaker demons that InuYasha's group encountered in those random villages never looked like normal beings. They were bigger and looked more fierce. It wouldn't be very wise to think that those 'wolf demons' were always in disguise as normal wolves. So, they couldn't even be wolf demons that do not have the power to transform into a human-like form. This point even counters the argument that they were demons.
Thus by this reasoning, I conclude that they were just normal wolves. But then, this is just my opinion. I guess it's only Rumiko Takahashi who knows the correct answer.