Jungfraujoch and Schilthorn Trips - question about pre-booking tickets

I would not book those tickets in advance.

On Schilthorn and First there is no advantage in booking in advance, as you will just queue up with everyone regardless. Booking ahead of time does not give you any privileges.

On the Jungfruajoch a ticket does not give you any special privileges either. Just as with all transportation in Switzerland the ticket is for the route, not a particular train. And just as with all transportation tickets do not sell out.
However the Jungfrau railway does sell "jump the queue" tickets that permit you to skip the queue at Kleine Scheidegg, and that thus guarantees you will go up on a particular services. Easiest is to just buy this reservation at the station the night before you go.

One tip: Any ticket office in the region can sell you tickets for any of the railways and cable cars. Foir example, if you are staying in Wengen and visiting the Schilthorn you can buy your ticket already in Wengen. Note that the Lauterbrunnen - Stechelberg bus is not part of the Jungfrau Travel pass, and neither is the cable car from Stechelberg to Murren. So if you want to take that route to the Schilthorn you will need a ticket Lauterburnnen - Stechelberg - Schilthorn. The ticket office can explain that to you.

Fun fact: I often see people queue up at the cable car ticket office in Lauterbrunnen. The smart person however just crosses the street and buys his ticket at the railway station...

In Lauterbrunnen I oftren eat in the Steinbock. And my favourite watering hole (with some good value pub food) is the Horner. Do stop over in Gimmelwald to sit in the beergarten at the Pension Gimmelwald.

In regards to the comment above about the line at the cable car office….when you have the Jungfrau Pass you don’t buy a ticket, the pass is your ticket. But for others reading this who don’t have a pass, the really smart person buys the ticket on their phone on the SBB app :)

For Jungfraujoch, if you have a tight schedule, where you’re trying to make a lot happen, you can purchase a seat reservation for 10chf per person and then just wait until that day when you know weather is cooperating to actually purchase your ticket. This way if the weather is bad you’re only out 10chf and not the whole ticket price.
https://www.jungfrau.ch/en-gb/jungfraujoch-top-of-europe/book-priority-boarding/

For First, I would definitely buy your ticket on your phone (SBB app) right before you head to the line, as the ticket lines are usually very long. As long as you’re not planning to do any activities up there (flyer, carts, etc) then you’ll just wait in the standard line waiting for a cable car, which will take probably 15-30 minutes. If you try to buy a ticket there, it will take longer.

For Schilthorn, again, buy your ticket that day once you’re in Mürren or Stechelberg and have looked at the webcams. No benefit to pre-buying.

Use MeteoSwiss, MeteoBlue and webcams to plan day to day. Sometimes one area can be fully in the clouds, while another is sunny, so the webcams are a major deal. We spend our summers living in Mürren and we live by the webcams. We’ve had pure 100% cloud cover all over the area with 100% Sun up at Jungfraujoch and vice versa, as sometimes the clouds will sit at lower altitudes leaving high peaks sunny, so if a weather app says cloudy, look at the webcams as well. Just Google “Location X Webcam” and they will come up for you. There are tons in the area.