Personally the world of I shall the Heavens also in the place Ninth Mountain, South Heaven. First I’ll steal the copper mirror then steal basically every good fortunes Meng has stumbled upon in every chapter.
I kinda get the impression that he'll find some other treasure and then proceed to use you as a stepping stone... For some weird reason, once in a millenia treasure are a dime a dozen...
Out of nostalgia, I’d go for Desolate Era and major in the fiendgod path, because the concept of an undying warrior going ahead with grit and passion just sounds cool. (Plus it’ll be less likely to depend on stuff like talent) The copper mirror sounds like it’s be fine, but getting more involved with the MC sounds risky. Are you really sure you want to get too involved in the schemes surrounding the Fang clan and Allheaven?
I don't think I've come across any cultivation stories with a world I would actually want to live in.
One of the modern cultivation worlds sounds the best. The fantasy and mysticality combined with the convenience and culture of a developed world.