I have to agree with your thoughts that knowing one of the people whom you have seen before does make for better Chemistry, relaxation, and a better experience. I know when I first started and worked at an agency long, long ago, it was get in, get the person off, robotic and if I was a man I would have felt pretty empty.  

However, that is the way they did things.

There is only one person whom I have did a duo with. It was with Jenna Raine whom I admire and have been friends with for quite some time. At first I was afraid it would interfere with our friendship.

However, with her being a dancer, and both us  being mature skilled professionals, it was a lot of fun. Especially with the whipped cream, chocolate, and cherries that we covered each other with, and the details, I will leave to your imagination.  

The guy had a fantastic time, and so did we. Kelley White

know one lady well and be sure that the 2 ladies know each other and have done duos with each other.

Lucky to be with a duo who I knew both, one far more intimately than the other. They do duos together and really are into each other. It was the ideal situation and one that was really fun. So be selective.

I did duos with my friend Jemma Lee, who sadly just retired.  We had great chemistry together and a very similar style.  We saw several people who had a very good time with us and said they had tried duos  before and it was awkward. I will say  just like solo adventures,  we can't read minds. Some gentlemen are really not into the activity between the two women as much as they are getting pampered by two women and having all the attention on them. Some enjoy more of a show.  
 I did agree to do a duo once with someone visiting who I had not met but she had great reviews. She was awesome but the session surely didn't feel as natural and comfortable as when with my usual partner