AndyCap The Hex will use the same sensor tech as the Square, but most likely with a finer spacing of the pads. Like the Square it will have two sliders of 15 elements each, at 90 degree angles to one another (but truncated to the overall outline of a hexagon). Since we expect the Hex will be smaller overall than the Square, the resolution can be somewhat finer.
You could cut down a Square to get a Hex, but this variation is more convenient in that you get consistent, repeatable results (which not everyone will have the tools to do), and as above, slightly finer resolution.
When we say you can use 8 sensors at a time, this is the number of unique I2C addresses that are available on each type of sensor. There's no limitation on using more sensors, if either (a) you use multiple I2C busses, or (b) you put custom firmware on the device with a different range of I2C addresses. Ultimately the main limitations to how many devices you can put on a single bus are the rise time of the bus and its total bandwidth. I would expect 20-30 devices should run relatively comfortably provided they had unique addresses.