e1x2 has 3 USB-C ports (power, USB-C computer also OTG, USB-C mobile OTG), e2x2 has 2 USB-C ports (power, USB-C data either desktop OR OTG mobile)
So, I guess the main diff for OTG is simultaneous desktop + mobile connection or dual mobile OTG at the same time (while being USB-C powered)...