WRA Alliance is smaller than MG, but I find it comfy, definitely not dead.
PvE and PvP are both active, I don’t really have a great point of comparison but I’ve seen guilds for both and know a lot of players in some WRA communities are engaged in both forms of content.
SW is most active in the evenings, it can be pretty empty in the morning/early afternoon, when it picks up it usually feels populated without being crowded.
Honestly the best advice is always roll an alt on both, spend a little time with each and see what jives best with you. WRA and MG are very different servers.