Hey there! If you're okay with fantasy and swapping out powers (though home ones can be regained), I play Minato over at melodiesoflife, a Final Fantasy-inspired game which has an active plot centered around saving the world and their own worlds by extension. The worldbuilding is extensive, and player actions effectively change the course of the story. It fits all your criteria, especially with backtag friendliness! As an added bonus, its AC is very simple and easy. Apps won't be opening again for a while yet, but test drive should be up in a couple weeks.