RPG servers add classes, skills, quests, and rare gear—Minecraft as a loot-and-level adventure. Some run on normal Paper with plugins; others need a full modpack.
Class balance and cash-shop power decide whether the endgame stays fun. If store gear beats earned sets on day one, expect fewer serious players later.
Confirm whether you join with a normal client (maybe a resource pack) or must install mods. That one detail decides your download size.