Linux

Before I could fully leave windows, I spent a lot of time being lost in Linux distrohopping and ricing without even fully understanding what I was doing. Without a solid setup to live in, Linux had a weird experimental feel and it got frustrating when I wanted stuff done.

Coming to your case, there are 2 different priorities here: daily driving and Linux proficiency. You're tied into windows for the daily driving bit for now so your main focus should be learning, and that probably won't need a dual boot right away.

First up is understanding why there are so many distributions. Linux is the kernel, the common skeleton that you can't use on its own. There are other modular bits that go on top to make a full fledged OS, and the choices of what those are is what makes a distribution. Learn more about the options available for the modular bits - the ones that you should concern yourself with for now are:

• package managers: the program responsible for installing and managing software. This is one of the main differences between the major popular variants of Linux(Debian, Arch, fedora etc). For example, on Debian and distros based on it, you'd use apt. That's why you would've probably used apt on Ubuntu, it's based on Debian.
• desktop environment: all the programs involved with the user interface - the main UI itself. This is a subjective thing and people use different desktop environments based on their workflow.

Once you get this modularity based perspective, distributions wont be overwhelming and vague. You'll understand why people are recommending mint or popOS:

• it's Ubuntu based and there are many popular Debian and Ubuntu based distros out there. You'll be able to get software easily and if there's some problem you need to debug, there's a relevant question and answer out there
• mint's desktop environment is cinnamon, which is simple, clean and not too jarring for people coming from windows

You'll also know, you can choose whatever you want as long as it's Ubuntu based for your learning phase. Only at that point I think it will make sense to dual boot. You can boot in for particular reasons instead of a vague "let me understand Linux". The reasons will be finding alternative software to daily drive, learning how to use the terminal or just getting comfortable with Linux in general. From there, you can find your own way or reach out to the community with questions specific for your use cases.