Would a doctor himself usually use the same specialist that he gives me a referral to see? is it in poor social etiquette to ask him?

If the need arose a doctor would often use that same doc. However, referrals are often guided by what insurance you have and whether their personal choice will take that insurance. You can always ask questions of a doc you you work with.

It's not good etiquette to ask personal questions of one's doctor. One's doctor may volunteer such information, but the doctor-patient relationship means the doctor is the one asking personal questions of the patient, not the other way around. A patient can ask for names of two specialists in the same specialty, and ask if there are any advantages or differences among the two.

Access to specialist services is in general limited and many times referrals are made on availability, not personality traits. You can definitely ask if your doc trusts the respective specialist. That is usually the case.