Hey the Classic Era realms are sparsely populated but you can find active communities depending on where ya look. Going off the Blue Post for CE Realm Connections:
Your realm Arugal is connected to two others (Felstriker and Yojamba). I play on Incendius in the NA PvP East Cluster that houses 5 realms total and it is also pretty small. The NA PvP Westcoast Cluster receives free transfers from other Classic Era PvP realms onto Whitemane while the NA PvE Eastcoast Cluster receives free transfers from other Classic Era PvE realms onto Mankrik. As for your second question, don’t worry. Classic Era realms are founded on not progressing down any of retail’s past expansions.