Gamerules in a realm should be available in the menu.

The settings in a realm's menu is too bareboned.

"In the Game settings you can edit the name of the Realm, set the difficulty of the game, game mode and reset the world."

It should possible for the player, who the "operator", to change pvp and show coordinates in the settings from the realms main menu. It is possible to change it ingame, if the operator enables cheats, but that disable achievements and that takes a rewarding part away from the game.