RealisticWorldGenerator have some important Permissions you will need to set to yourself and maybe also your users.
If you want to give an user all Permissions you have to give him following Permission: rwg.*
/rwg and /rwg help - rwg.help
/rwg version - rwg.version
/rwg preloadConfig - rwg.preloadconfig
/rwg setOneBiome - rwg.setonebiome
/rwg setWorldType - rwg.setworldtype
/rwg pasteTree - rwg.pastetree
/rwg pasteStructure - rwg.pastestructure
/rwg installationhelp - rwg.installationhelp
Using the Actionbar to show Biomes - rwg.actionbar
Get Informations on Join - rwg.admin