<<"2. 3 days for Lauterbrunnen region to cover Wengen, Murren, Grindelwald, Pfingstegg, Jungfrau, Schilthorn. ">>
<<"A follow up clarification - is 3 days not sufficient or more than enough
for the places that I wish to visit in the Lauterbrunnen region?">>
<<" Hopefully we'll get such clear weather as well!">>
Your own words are a partial answer. If clouds and fog cover the mountains, you won't be able to cover anything. ;-(
By allowing at least 3 days in the region, you have a better chance, because the weather can change fast, and frequently. It comes in layers, too. Foggy below, clear above or vice versa. Contingency plans are desirable. From Thun you can go to Brienz, Bern or Luzern, or Brig or Zermatt or Montreux for example. September is probably the best month for good weather in the Jungfrau region. Actually, for all of Switzerland, as well. I have booked my flights for a couple of weeks in early September, expecting to spend time in the Alps.
It is very difficult to answer a question with the word "cover" in it. Using the word "visit" is not much better.
What do you hope to do when you "cover" or visit something?
Would you hike?
That hike is the one I was on when I took the picture you noted.
In this section, there are several hikes near the Jungfrau:
On any of those hikes, if you are a serious photographer, you will pause to look and take pictures frequently... so they may take a bit longer than is suggested.
If cover means - "get off the train/cableway, etc., put two feet on the ground, and catch the next transport onward," you can do it all in less than two days. By squeezing it together as much as possible, you might make it in 1 and 1/2 days. Depends on how early you want to get up and on the way. Some of the mountain transport does not run late in the day; check the timetable to work out your schedule.
If the principle purpose of "cover" is to ride the transport and look out the window, the timetable will guide you and you won't need much else.
In fact, even if you have something else in mind, the timetable is your first resort to answer questions about "enough time."
If you use a map to locate the towns:
and zoom in to find the transport, and turn on "Traffic" under "Points of Interest" you can figure out routes that match your interests.
The links for the region and towns within it can give some help:
You can spend weeks enjoyably in the Jungfrau Region.
This link will give you a little reading to help you think about: