Lauterbrunnen is amazing. We also really enjoyed Gruyere and the Caillier chocolate factory. I don't think you need a car. Get the Swiss train pass and that will allow you access to all public transportation, e.g., trains, buses, boats, trams, etc., plus you get discounts at museums. Get the first class pass. It doesn't cost that much more and the solitude is well worth it. If you go the train route, download the SBB app. It is great for managing transportation. And if you are Latter-day Saints, a trip to the Swiss temple in Bern is awesome.