I can clarify definitively some points I wasn’t entirely sure about until today:
Sony A7sIII uses a new 12MP BSI sensor. There is no indication it uses the 48MP Quad sensor (downscaled to 12MP).
Sony A7sIII has no active vent. It only uses a pure new passive cool system.
The camera has two slots. And each slot is capable of taking SD cards and the brand new CFexpress Type A cards.