Sci Fi - protagonists get teleported to worlds with different hardness

[Álvaro]

Plot details: For reasons that I cannot remember, protagonists get teleported? to worlds with different hardness:
- world 30/70 - high gravity, very difficult to survive
- world 40/60 - I think this was actually the Earth
- world 50/50 - cant remember anything about this one
- world 70/30 - exotic world where the protagonist lives like in a tribu with a lot of women and has lots of sex, on the other side, people needs to be sacrificed for like a dragon or a giant lizard?

Book read around 1990-2000. Book probably written between 50s and 80s.

[Ky]

If you're still around or you come back to this post, I suggest you go through a list of the books written by Robert A. Heinlein or Piers Anthony. Something about your description made me think of these two, but I can't think of a specific title.