Hey there – sorry for the delayed response here. The B SoM will be available in the upcoming weeks, and we expect the A and X SoM to become available in 2020. Although the hardware design is in a relatively mature state, we are still refining the Mesh networking protocol and network management tools that we believe are necessary for product creators to successfully deploy Particle Mesh networks at scale.
All SoMs will feature a pin compatible design that allows for interchangeability for mixed connectivity deployments.
One more question, in the datasheet what is the difference between VCC (System power in, connect to the +LiPo or supply a fixed 3.6-4.2v power) and 3V3 (System power in, supply a fixed 3.0-3.6v power)?
VCC is used to supply large currents and high and wide voltages, for example to power a cellular modem. 3V3 provides low current stable fixed voltage for systems MCU, logic GPIO, memory. Let me know if that answers your question!