Best base to explore Switzerland & France

You could stay in Basel, Switzerland and take day trips to Colmar and Strasbourg. I did this in 2021 and it was easy to do. If you have any interest in Germany, Freiburg also makes a great day trip from Basel.

My trip report has some info. on the day trips:

https://community.ricksteves.com/travel-forum/trip-reports/still-dreaming-of-switzerland-a-trip-report

Good luck with the planning.

Thank you very much for your reply, Carrie.

I thought of Basel as a stop on a day trip to France but not sure if it's worth staying 5 nights in. Don't know anything about Freiburg so will look into it. I'm open to any scenic and charming places that are close enough to other places worth visiting.

I'm enjoying reading your trip report! :)

Alsace & Chamonix are on opposite sides of Switzerland, and the mid-point is too far from either for day trips.
You could easily stay in Alsace for 5 nights, there is plenty to do. Colmar is a good base, with easy access to Strasbourg, to the surrounding villages, to Mulhouse (worthwhile if you are into car or train museums), and decent access to Freiburg.

How about all 8 days exploring the Bernese Oberland as there are a few different valleys to explore (Kandersteg and Meiringen) besides the Lauterbrunnen valley. If you enjoyed Zermatt, you will also enjoy the Bernese Oberland. Everyday may not have perfect weather

There are a some things to do around Sigriswil. However, you will have an extra bus to Interlaken to catch the trains to the valleys. Spiez is a short train to Interlaken and closer to Kandersteg. I had trouble finding the right accommodation there and ended up in Interlaken near Unterseen for 7 nights,

I was hoping for some suggestion as to whether it's worth staying in Thun or Neuchatel which is close enough to France or stay in Wengen

I am not quite sure I understand you. Are you able to find available rooms in Wengen? If your goal is to explore the Berner Oberland—particularly the Jungfrau Region, which is what most people on this forum mean when mentioning the BO—Wengen would be a more ideal base than Sigriswil.

Also, Sigriswil is just a 27-minute bus ride from Thun, so if you're considering establishing a second base in Switzerland, it might not make the most sense to move from Sigriswil to Thun.

Thank you all for your replies!

The reason I plan to stay in Sigriswil for 3 nights is because it was only available for that time and is not that far from all the places in BO we'd like to see. I can't find a good accommodation that has good views for some reason and also close enough to places I'd like to see. Most of the good hotels in BO are all completely booked too, so I thought Thun might not be a bad base to visit both France (over two hours) and see some more of BO in case the first few days we encounter bad weather and need a little more time there (Dave).

There is still an availability in Wengen but then it would be too far from France. I've also looked into many areas including Spiez and haven't found anything (SwissNomad).

I just can't seem to find a way to see Switzerland and France with having bases only in Switzerland that are good enough.

If it's a fruitless effort, I don't want to waste any more time ( wasted enough already) and either plan to stay all 8 days in BO (Dave) move on to France for the rest of the time (Balso). But I don't think that gives us enough time in a Switzerland where we'd like to spend most of our time on this trip.