Welcome to Linux! I might say that the package system doesn't matter too much, both are popular and more often than not large distributions have (almost) the same packages.
The things that you should worry about are:
How stable are the releases? (How many times I'll have to fix problems that I don't want to investigate)
There are Linux distros that are on the "bleeding edge", meaning they get releases very often but sometimes things break and you will have to fix them either by using a backup or troubleshooting. (This doesn't happen often though IME)
But more stable distros tend to receive new updates later than everyone else.
How adapted is the distro to what I want to do?
If you want to use it as a desktop for graphic tools like office work, graphic design or gaming, it will direct you towards a group of distributions, rather than the other.
It is also important to consider if a specific application that you want to use is available or not. (In many cases it should be, but if you don't want to tinker, having your system working out of the box should be a priority)
How compatible is it with my hardware?
If this is a laptop, I'll suggest searching with the laptop model and the linux distro terms, seeing if there is a wiki page for your specific computer; documentation in the linux world is essential.
Otherwise, there's a thing called usb live linux that can turn most usb pen drives in a live running OS, allowing you to test and trial how compatible the distribution is.
Finally, some advice:
Figure out your backup method soon and test it. Backup before trying something new. (Top priority)
Use flatpak, appimage or snap to install applications. I ordered by my personal preference, but sometimes applications are not available in all formats. Few applications like Gnome Software or KDE discover will simplify your life managing apps as if you were using a phone.
Be easy on yourself and have fun. Sometimes this world can be frustrating, but I'm sure the answer is right around the corner, you just need time ;)
My way of seeing it is similar to yours: If you're interested in learning NixOS, then go for it, but if you need an OS that gets out of the way but still gives us plenty of customization choices then I'll rather go for something else.
The thing is, I want to have audio in my system without having to spend two weeks learning a new declarative language plus pulseaudio, alsa, pipewire, etc..
My time in this blursed earth is short and I want to focus learning what I care about.
In other words: There's people that like crafting their own tools and there's people that go to the shop and buy some, but NixOS feels like that youtube channel "Primitive Technology" where the guy builds the tools out of raw materials, including the furnace to melt iron, the casts, buckets, pliers, table, etc.
My experience in India is probably largely anecdotic, but everything went through an app, including the prescription, analysis and xrays. It was pretty impressive because I've got it almost instantly.
Appeal to emotions, rather than logic, and if you pull the right lever, that person will get a bias confirmation, feel smarter for knowing something everyone else doesn't and in some cases, feel less insecure for not knowing enough.
I've met people that have a degree or that are even teaching and have the worst baseless believes. It's only a matter of getting to your levers.
Welcome to Linux! I might say that the package system doesn't matter too much, both are popular and more often than not large distributions have (almost) the same packages.
The things that you should worry about are:
Finally, some advice: