I mean, there's basically no good economic reason for any space colonization whatsoever, outside of potentially the asteroid belt. Neither Venus nor Mars have significant resources that aren't found in similar abundance on Earth, where extraction is orders of magnitude cheaper and easier. Tourism would be an industry, but it would almost certainly be an extremely niche business similar to OceanGate's Titanic visits, Blue Origin's launches, or stuff like Dear Moon. Rich people might pay very well to go visit Mars or Venus or the Moon but that pay certainly would not be enough to offset the trillions of dollars (yes, trillions) and decades that true colonization would take.

With that in mind, discussions of real space colonization are entirely theoretical and probably always will be, at least within our lifetimes. It is very conceivable that humans will land on Mars and maybe establish permanent research outposts there, on the Moon, or hypothetically Venus. But those would be far more similar to something like the ISS-- hosting a rotating crew of mostly astronauts and the occasional space tourist. I find it hard to imagine an economic case for anything more anywhere in the solar system within a reasonable span of time.

The theory is that since most of Venus' atmosphere is CO2 at this level, the breathable atmosphere of a human habitat is actually bouyant, which would make suspending a colony much easier.

Doing something like that on the scale of a research presence like the ISS is within the realm of current technology-- but you are right that doing so for a whole city is not technically possible at the moment-- nor is true space colonization in general, I would argue. There's a lot of unknowns and unsolved problems.