Suggestions for central/home base to stay Aug 2021

Please clarify: you want one base for visiting all those locations in Switzerland? Will you be traveling solo?

I would like one base/two if needed but no more; I am traveling solo. Thanks

It is challenging to properly visit all of these locations from 1 or 2 bases.
Technically, if you base yourself in Spiez (which is a fine town), you would be on Lake Thun, less than 1 hour from Lauterbrunnen valley (for Berner Oberland), and not that far from Gstaad either (but there is very little of interest there, besides the scenic "golden pass" railway). Zermatt would be 2 hours away, so a long day trip (not recommended, but not impossible).

Then, to visit the upper Engadine you have to stay there (e.g. Pontresina or Samedan, avoid ugly St Moritz), it is too far from anywhere else.

Same for Ticino.

Brig would be even more centrally located than Spiez, but I don’t know what the town is like—-we have changed trains there many times, but have never left the station to explore the town. I would be tempted to stay in the nearby carefree village of Bettmeralp, up on the mountain high above the valley. It would be a cablecar ride plus 10-15 minutes on the train from Brig.

This would work as a base even for visiting Ticino. Brig to Locarno is 2.5 hours by train, using the scenic Centovalli railway from Domodossola to Locarno.

For visiting the upper Engadine look at Sils Maria or Pontresina rather than St. Moritz. Balso is right about its lack of charm. And this area is too far from either Spiez or Brig for a daytrip, so it should be base #2.

I stayed at Brig before. It's a nice small town with a real, local community. Most tourists don't leave the train station but I find it a convenient base to explore the region. Go for it!

Thank you so much Balso, Lola, and Barkinpark for your suggestions. I will rethink my home/base locations and number of home bases.
I hope you'all have safe travels this summer and fall.
Judith