Balmung is indeed the most populated RP server. It is so populated it is even overpopulated and character creation and transfers to Balmung has been blocked until further notice.
Even before the complete lockdown it was almost impossible to create a new character on Balmung, except for about half a minute right after maintenance.
Of the RP servers you can actually get onto I'd say Mateus(NA) and Omega(EU) are the most populated and active.
Thank you so much for your reply!!
I created my character in Mateus for the very reason. Also, I was wondering which version is better, Steam or Retail?