I've only been to Jungfraublick and that was twenty years ago, our very first overseas trip with the caravan. From memory the site was very good but the pitches were a bit small and cramped. That aside, it is located on the edge of Interlaken and very convenient for Lauterbrunnen and Grindlewald. Apart from one day we never did more that about 12 miles in the car on any day. The trains and cable cars will take you to most places with ease.
The site suffers (or did 20 years ago) from a bit of aircraft noise from a military air base only about a mile away. Conversely, one could sit at the caravan watching them skydiving in an evening or weekend. Personally, aircraft noise isn't a problem to me.
The whole area is spectacular but we found that (despite what I wrote earlier) there are not that many roads up into the mountains. Consequently, in following years we went to the French alps where mountain roads are common. Like you, we are now Francophiles.
We'd like to go back to the area if it wasn't so very expensive especially with things like the vignettes that are needed for both car and caravan if any travelling, no matter how short a distance, is done on a motorway.
I'm sure you will enjoy the area, there are lots of places to see and things to do that you don't really get elswhere in such a concentration.