Most of the Era realms were connected with others that share their server type and region. RP realms were exempted from these connections. In addition to these realm connections, Blizzard set up two realms to receive free transfers: Mankrik for PvE (NA East) and Whitemane for PvP (NA West). I play on one of the PvP clusters in the East that holds together the realms Benediction, Faerlina, Heartseeker, Incendius, and Netherwind. Its a small community but our guild has levelers doing dungeons in all ranges.
My advice for anyone looking for a place to play is to roll a level 1 on any prospective realm and chat with the locals to get a better idea of the server’s community/culture.