Hi there! I’m new to Kbin, so bear with me:

1. I wouldn’t call Pop and Mint “windows-like”. Both are customizable to a great degree, and Pop definitely starts off as being “fresh” and “new” feeling, IMO, compared with the tried-and-true-desktop-metaphor of Windows. But Mint, like Pop, is flexible. Note that I’m a Debian user nowadays, but credit where credit’s due: both Pop and Mint are great choices.
2. I don’t know if there’s any good resource that compiles a list of what makes a distro unique. Every attempt at doing so has led toward more questions than answers IMO. Best teacher is experience, either your own or the experience of others. That said, a distro is a combination of package manager, desktop environment, associated applications, upstream and downstream packages, documentation, and most of all- community. Folks overlook the community when picking a distro, and get into trouble when their distro choices don’t sync up with their idea of community. Debian and Ubuntu may be similar on a technical front but are very different communities with differing goals!
3. Finding out what’s missing gets back to that community aspect, but also experience. Every distro is different and any attempt at cataloguing differences would quickly go out of date. Really, the best teacher here is experience and community- I know that sounds like a broken record at this point.
4. On GNOME based distros, I really appreciate Pop Shell’s tiling. Beyond that, KDEConnect/GSConnect brings mobile confluence to Linux desktops and is a must-have for me. It’s great when the music turns off when I get a phone call- that sort of thing.
5. Depending on the distribution, I usually install mpv right away, and whatever I need to privately watch YouTube videos. FreeTube is a great choice for this. Beyond that, I usually just get cracking on importing my drives/partitions/etc and setting up my editor (I use Kdenlive but I make videos- you might not need that sort of thing depending on your use needs).
6. Don’t avoid installing qt libraries if your application needs them. This gets to a bigger issue though- don’t just do something because someone on a forum tells you to. That includes me here right now- ask questions like you’re doing right now, but also stay skeptical of easy answers or the algorithm-driven bombastic responses of “stop using X use Y instead”. That crap ruins Linux for so many of us.
7. Do what you like! I like Debian and it’s gotten much better as a desktop user. Before that I used Pop for years. Before that Arch. I go with the flow and I’m not afraid to change things up- that’s probably the moral of the Linux-desktop story! :)

Good luck to you!

@ernest Thank you! I take it you work on this site, if so thank you and I’m sorry for being such a newb.