During the time I was working on the LinnStrument Darker Mod, I had a lengthy conversation with Roger about sensors. He said that the ERAE Touch uses a force-sensing multi-touch trackpad, which has a fast scan rate at the cost of sensor sensitivity and density compared to its size. The LinnStrument, on the other hand, uses force-sensing resistors arranged in a matrix grid array with a fast scan rate and high sensitivity at the cost of sensor density compared to its size. There are also spacers separating the rows, among other design choices.
It has various hardware modifications and multiple custom firmware. There are more that are not included in these lists, but I do not have time to crawl through the KVR Audio Forums and GitHub repositories to include them.