@FE Hoppy
I don't think the "E" is for Electronic (FADEC) because the -8C5 variants of the CF34 on the CRJ-700 and subs are also FADEC controlled.
IIRC, the E, C and D, when it existed, were for Embraer, Canadair and Dornier versions respectively. (there was an -8D3 for a while on the Dorniers) GE now seems to be associating the "A" designator to the Chinese ARJ21