Printsize, you said the Gadgeteer “letters” are hard to understand. Actually, they’re no harder to understand than any other connection pattern - well perhaps not as simple as what you’re used to with Arduino, but it’s not too much different.
Each socket has 3v3, 5v, and GND. So that’s similar to e-block except you get both voltages, bonus for those devices that need 5v to operate.
Then you get a set of IO pins, either for specific purposes or general purpose IOs. This is better than e-blocks because you have a larger number of IOs for devices that need more than just a single data pin, for instance an SPI device - on e-block you’d need multiple 3-pin wires to run those, but you have them all in a Gadgeteer S socket (plus some to spare!).
Page 5 in the module builders guide has the master list of the layouts. If you want a set of general IOs, then you want an X or Y socket; if you want Analog In, thats an A socket; I2C is an I; UART is U or K (K has handshaking); PWM is P; etc.
The great thing is you pick up a module, and you know what possible sockets you can plug it into because it’s labelled. There’s no question whether you have something that’s connected the same way or not. Unlike the situation where today if someone decides to use a 3-pin connector and decides to put GND and 3V3 on opposite sides to what GHI decided, and if you don’t check and plug it in your sensor or Fez becomes toast.