TL;DR 1.2mm. CEM3. Purple.
Multiple PCBs are available. All are 1.2mm thick. All PCBs use a CEM3 substrate which is marginally more flexible than FR4, which is the traditional keyboard PCB substrate material.
The "-nu" versions have a JST connector that supports the Universal Daughterboard standard. You can also buy a purple USB C daughterboard via this buy. The "c" versions have a USB Type C port onboard, and these will only work with boards designed to work with a USB Type C port - not USB Mini B.
The h60 supports a 3-1-3 split spacebar.
All PCBs have MX- and Alps-compatible switch footprints, in-switch solderable LED capability, RGB underglow, and will arrive with the smallest premonition of love from yours truly.