I like that it doesn't manage the python/venv installation. E.g. rye creates a .venv for every project and in case of packages that are large, that starts to add up as more projects are added. With poetry, I can separately create a "common" virtualenv which I can use with bunch of throwaway projects; this is of course assuming that the version requirements of these projects do not clash - if they do, I can always create another virtualenv.

With rye, I activated a virtualenv and then created a new project, it proceeded to setup its own .venv within the project instead of just using the one that was already activated.

I would consider both of those flaws of Rye, not Poetry. Python package managers not written in Python will by definition have less contributors, and to me, they make Python look like a toy language (you can't write a package manager, a fairly trivial program with the exception of dependency management, in Python - what can you write then?)

As for managing Pythons, I would consider this to be orthogonal to packaging, and the default system Python is often good enough.

Yes. You choose a standard version (usually the latest stable 3.12 currently) that it downloads at setup or it downloads and sets up the pinned version from your pyproject.toml.

Could you explain futher? By 'environment' do you mean platform?