I never heard of Superman of Earth-A, but I'm also a noob. An exception may be worthwhile...Rao's call.
I'm actually not opposed to Legion or JLA being included after a while...but we have a lot to catch up on first. I don't think we should make more materials canonical until we've caught up on, say... DC Comics Presents. The encyclopedia has grown tremendously in the last year or so, but there is still much to do.
Actually, this would also be much easier if my Superman Quiz Book by Bruce Nash (1978) could be considered as a source of information.