This is a replacement of the original electronic shocks. The Touratech Evo shocks work with the D-ESA system on the bike to retain but improve the factory electronic suspension.

Generally speaking you want a stiffer setup in soft sand. However, for a loaded adventure bike I would tune to the rider's preference since soft sand can be a lot of work on these bikes!

That is a very common response from riders who fall within the weight specifications that the OEM suspension was designed for and have never ridden with a set of high quality and properly tuned suspension. The stock suspension on these bikes is very good if you are of average weight and don't ride the bikes hard.

Neither actually. The spring rate can be customized for the rider so if you are much heavier or lighter than average that is a good thing. Also, the valving in the shock combined with the different piston and electronics allows it to respond faster and more accurately to all terrain.