Priority boarding on Ryanair flights is a curious thing. Theoretically, the whole plane could pay for priority boarding and everybody would stand in the very same queue.
I personally never used it and usually there’s just a handful of people using the priority boarding. In fact, I usually fly with my girlfriend and quite frequently we simply wait till all passengers boarded the plane. Usually, we have no difficulty finding adjacent seats. Anyway, I prefer to wait and be separated from my GF for a couple hours than to wait in the queue for half an hour.
Priority queue is just another way of Ryanair making money on those who are ready to pay the extra fee to feel a little bit better. Which is good because that makes my tickets cheaper.