My experience this year walking both the Variante Espiritual and Camino Sanabres was that the Xunta albergues on both routes were never full, even when places that could be booked were not showing any vacancies. That is, of course, no guarantee that there will be a place when you walk, but it might give you some confidence that beds will be available. It might be more a matter of finding where they are than whether they exist.
I haven't stayed at Hebron, but where I have wanted to stay at a particular albergue that didn't take bookings, I have made sure that I got there relatively early in the afternoon. The irony is that many of these places remained relatively empty, even on the CP. Again, no guarantees at the time you are walking. As for there being a long queue, if you know how many beds are available, it will not be difficult to work out whether you can expect a bed for the night. There would be no point queuing otherwise.
Most places I stayed had power points for each bed, or close enough. If I booked, I would always let the property know that I needed to be close to a power point so I could use a CPAP. In only one or two places did that mean I had to be given a specific bed because there weren't power points near every bed. It was never an issue getting access to a power point.
I stayed at
Casa da Fernanda. There was no difficulty with power points points, although you might find you are sharing one with the adjacent bed. I cannot quite remember how that worked, just that it wasn't an issue. I didn't stay at Ninho.