Fact
Ruleset rules (Blizzard ruleset article): rulesets replace realm selection; grouping, dungeons and raids are limited to the same ruleset; a character cannot change ruleset (a new character is needed); collections and Legacy Points are account-wide; the PvP ruleset allows characters of one faction only, while Normal, Roleplaying and Hardcore allow both.
Sources
- news.blizzard.com/en-us/article/24302070/updated-10-22-choose-… — Blizzard News