are clans like factions in wow?

[Anova]

To my knowledge, Leviathan is among the 10 most populous servers. Faerie, Siren, and Exodus all exceed 30k accounts though and are the most populated NA communities.

As for seeing players in the field, most players have spread out in to different zones. Limsa Lominsa and the surrounding fields are one of the least populated areas. You might notice a large congregation of players in middle la noscea and western la noscea for the Lightning Fate events in the next two weeks though.

As far as popular maps go though, western la noscea is a common fate-grinding spot for levels 10-20. Western Thanalan is common for levels 1-15, and you will likely find 5-10 players during FATE events there. Central shroud will also have some, but fewer than Thanalan.