There is another Knights Templar castle in Ponferrada and it isn't far from the Picos (western part of but south of them). If you get bad weather you might actually be glad of a stint south of the Picos to enjoy the dry sunshine.
https://castillodelostemplarios.com/
We visited it last year. It's not Ghent, Leeds or Edinburgh, in the sense that it is mostly just a castle that you walk in and around but it doesn't have the audio tour and the exhibits are patchy. The library is pretty well done, and the oldest part of the castle was under refurbishment when we were there. The city itself is Ok and there is a Templar Hotel which is a very decent hotel. It's called Hotel Temple.
https://www.hoteltempleponferrada.com/
A
must see if you are going towards Soria is the set from the last scene of
The Good, The Bad and The Ugly, called Sad Hill. If you have Netflix then there is a documentary on the labour of love by enthusiasts to restore it: SAD HILL UNEARTHED. If you or any of your group are fond of what has to be the best western ever made, it's a really worthwhile pilgrimmage. It's on your way, south of Burgos just off the N234 in a small but beautiful town called Santo Domingo De Silos. It has a beautiful Abbey where they used to televise Gregorian Chants on the TV in Spain in the 70's.
When we went there they'd only just finished the reconstruction. I was expecting a rather drab and neglected village and set but BOY! was I wrong.
https://www.youtube.com/watch?v=BPYoFenZl0w
https://www.youtube.com/watch?v=BrEQPe7l6zU
We found it quite magical, free (no entrance fee) and we stayed here:
http://www.hoteltrescoronasdesilos.com/es/santodomingodesilos/index.asp
Slap bang in the middle of the town. The food is excellent, the hotel beautiful (you can park your bikes against the wall with permission, perfectly safe overnight), there is even night life in the form of late bars and a little night club should you feel in the mood to shake your stuff.
You can either ride the 2 miles or so to the set along a dirt track or you can walk it. The hill to get back up afterwards might have you wishing you'd ridden but if you have had a few long days in the sadlle, you might actually be grateful for the stretch.
To get down to Burgos (and then Soria) from the Picos I'd highly recommend the N623 as opposed to the N627.
Canfranc is now open. Again, it was a pilgrimage we did on one of our tours. We did it just before the major work started and we roamed for a couple of hours around the place and stayed in Jaca. I believe they have removed most of the old weed covered rolling stock which you could climb all over and they have removed the rolling stock within the sheds and demolished most of them (don't quote me but I saw some posts on FB about it). The sheds were mostly closed when we went anyway but a few of the machine shops were open. It's a shame they have removed the decaying rolling stock because it gave the place a real atmosphere. I am led to believe it now costs a few euros to roam around, but not sure how restrictive it is.
If the weather is foul then I'd advise avoiding the N260. Rather hop over the border into France where you will usually have better (and safer) weather to ride in.