Advanced booking hotels Jungfrau region September?

I started out planning to do the the Via Alpina on the Activity Workshop schedule. I've now decided to bail out at Grosse Scheidegg. Current plan has me coming down from Faulhorn September 30th. I have the TJR book and I'm thinking to bypass the Grindelwald, Lauterbrunnen area and sneak up on Murren from behind. One thing that has dogged me in planning this whole trip is the need to book lodging in advance. I have every night booked from Sargans to Faulhorn. So much for spontaneity. Lately I've become suspicious that booking for weekends is a good idea but during the work week not so necessary. I'd like to hear any thots anyone has on the lodging situation from Widerswil to Murren. Looks like the whole trek will be week days with the first night being Sunday at Saxeten.

I've hiked the Swiss trails you are intending to. Nepal as well. The only common factor is that you can hike for weeks without carrying very much weight. Other than that Switzerland is entirely different. There is no cultural component and no sense of being away from anything. Think of it as a very big park. In places a theme park.
I can sympathize with your feelings about advance booking. The problem is if you arrive some place like Murren without a reservation the only rooms left could be $500 +!+! I think once you start making reservations, as you have, you may as well continue. You're already tied to a schedule. Flexibility isn't an option unless you are willing to to cancel, lose deposits, and run the risk of not finding economical stays. Even on weekends, even on the shoulder of the season, and even on lesser done sections. Give up and play the game. The section you're asking about is only a couple of slack days on mild trails. And there is really no choice about where to stay along the way. Relax. Take a book.
I think you were on the right track when you started out looking into Walserweg. That you couldn't get much info on it is encouraging in itself. Probably no glamourous big name mountains or need for a detailed itinerary.
Happy trails