I have no experience with Actus-mini but have visited Jungfrau and Matterhorn many times. This will be wildflower season, in the mountains they grow low to the ground. In FF shooting, wider angle, in the rang of 16-24 mm can be very appealing for capturing the scale of the mountains. If you are truly going for panoramic shots, maybe stitching will suffice. Otherwise, your lens set seems too long. If the actus has a FF back, I think you need wider, as I said from 16-24 mm.
These areas provide great photo ops, but realistically, if you are just passing through, you may not be there at the best times of day. In fact, the trains and lifts don't allow for really early morning photo access. As you may know, you can take trains high into the mountains and you will have access to vistas near the stations. For example, in Zermatt, you can take the train from Gornergrat Bahn up to the Rottenboden and Riffelsee stations. From either, you can walk short distances to vistas of the Matterhorn over a shallow lake. Similarly, from Lauterbrunnen , you can take the cog railroad to Kliene Sheidegg, the midway point on the trip to the top of the Jungfrau. From there and other points, you can photograph the Jungfrau, weather permitting, crowds, permitting, etc.
