MOX SFP and Ethernet modules


I’m very interested in backing the MOX project, but I’m having a hard time understanding how to get the SFP module, especially since it says it’s not compatible with the Ethernet module: is there an option to swap those two for the backing?
Also, I’m not really understanding the purpose of module B and how the WiFi gets added… It seems that by buying the single modules you don’t get the WiFI, but then there’s no mention of it as a perk to be added.

Anyway, my general understanding is that what I want is modules A B and D with the WiFi, which is the “Power WiFi” (same thing as the MOX Classic?) with C and D swapped, is that correct?