My new user experience has been awful and I'm not sure what I'm doing wrong. Could really use some guidance.

I recently tried switching from Arch to NixOS and the experience I had can best be described as apalling. I have not had a new user experience this bad since my first dip into Ubuntu dependency hell back in 2016. I'd like to preface this by saying I've been a Linux user in one form or another for almost half my life at this point, and in that time this may well be the most I've struggled to get things to work.

Apparently they have this thing called home-manager which looks pretty cool. I'd like to give that a shot. Apparently I have to enable a new Nix channel before I can install it. I'm guessing that's the equivalent of a PPA? Well, alright. nix-channel --add ..., nix-channel --update (oh, so it waits until now to tell me I typo'd the URL. Alright), and now to run the installation command and... couldn't find home-manager? Huh?? I just installed it. I google the error message and apparently you have to reboot after adding a new nix-channel and doing nix-channel --update before it will actually take effect, and the home-manager guide didn't tell me that. Ah well, at least it works now.

I didn't want to wait for KDE and its 6 morbillion dependencies to download, so I opted for Weston. It wasn't a thing in configuration.nix (programs.weston.enable=true; threw an error and there was no page for it on the NixOS wiki), but it was available in nix-env (side note: why does nix-env -i take upwards of 30 seconds just to locate a package?), so I installed it, tried to run it, and promptly got an inscrutable "Permission denied" error with one Google result that had gone unresolved. Oh well, that's alright, I guess that's not supported just yet -- I'll install Sway instead. Great, now I have a GUI and all I need is a browser. nix-env -i firefox gave me the firefox-beta binary which displayed the crash reporter before even opening a browser window. Okay, note to self: always use configuration.nix. One programs.firefox.enable=true; and one nixos-rebuild switch later, I'm off to the races. Browser is up and running. Success! Now I'd like to install a Rust development environment so I can get back to work. According to NixOS wiki, I can copy paste this incantation into a shell.nix file and have rustup in there. Cool. After resolving a few minor hangups regarding compiler version, manually telling rustc where the linker is, and telling nix-shell that I also need cmake (which was thankfully pretty easy), I'm met with a "missing pkg-config file for openssl" error that I have absolutely no idea how to begin to resolve.

I'm trying to stick with it, I really am -- I love the idea that I can just copy my entire configuration to a brand new install by copying one file and the contents of my home directory and have it be effectively the same machine -- but I'm really struggling here. Surely people wouldn't rave about NixOS as much as they do if it was really this bad? What am I doing wrong?

Also unrelated but am I correct in assuming that I cannot install KDE without also installing the X server?