Forget "habitable super earths" how about a nice "mini earth?
Core of iron, more dense than earth, so it's smaller but has the same gravity. Then a crust like earth and atmosphere. I guess the atmosphere would need to be deeper to have enough pressure?
I wonder how small you could go?
@futurebird What about moons instead? There's a lot of possibility for moons around gas giants perhaps. I recall in some story (I think something by Asimov?) there was a rogue star known as Nemesis that they visited. It ultimately turned out to miss the Sol system, but within that Nemesis system there was a gas giant that sufficiently protected its moons from the worst of the radiation from its type M star. They had setup a colony or something I think?
(I can't remember what I read. Oof it has been a long time.)
With the right conditions you could probably get some fairly tiny Earth-like moons I think?