If you like the idea of asdf, I would recommend looking at mise. It does all the same things (and more) and is much more performant in my experience.

I have been trialing pacdef recently. It sounds like it would do what you’re looking for.

The guided installer will resize your disk volume and set it up for dual boot by default. It’s Fedora based and uses KDE Plasma which is a great user experience IMO. Admittedly, I only booted into it to briefly kick the tires but the install was a pretty smooth process. This page details what features are still missing so I’d suggest looking there first to ensure you’re not missing anything critical. For me, missing USB-C monitor support is a deal breaker.