more on-topic, the below links to a thread that has some useful information about Classic Era realms PvP and otherwise:
tl;dr: Whitemane in the NA PvP West and Mankrik in the NA PvE East will likely be the most populated (unsure of the faction split). There are other communities outside of these clusters though and I encourage you to roll a lv 1 on any prospective realm and try chatting with the locals to find the place that’s right for you.