I see quite a few people put him after either Astra or Kayo but how much can his abilities do?

“You have the ability to rift-walk and you stay here? What a shame, there are so many better worlds out there..." - Viper voiceline. Does this imply that he can travel through worlds like Astra or is it just Viper lack of understanding on Yoru’s power? Or “worlds” doesnt actually mean a whole different world? I feel like theres more to his power but im too dumb to have my own theories on it.