Often if you can make it past the first interview you don’t get caught unless a workers comp claim gets filed. The place I work we had people * in training* come in smelling like weed, a few others smelling like booze, and one came in very obviously high on coke. From what I remember the only one who got fired was for cursing someone out. Even past that, we’ve had a couple of members of leaderships who were alcoholics who regularly drank on the job, and there was always at least one person smoking in the parking lot.

All depends on employee tolerance and employer need, really.

I spent about a year in NixOS, and my main desktop still has it, though mostly out of laziness. I did end up switching back to Arch, mostly because if there’s anything you need that isn’t in the Nix repos it’s a pain to install. The other big issue I had was the lack of documentation, so you’ll be figuring a lot of stuff out completely on your own, because Nix works differently enough to everything else that a lot of general Linux resources just don’t apply.

If I had a recommendation for switching to nixos, I’d probably say use the Nix package manager on Arch for a while first, and just slowly switch everything to Arch. It’ll get you more familiar with everything, and then you can make the switch more easily.

Very, I only really use my mouse for playing video games at this point. You don’t really NEED to use Emacs/Vim/etc, but they do help a lot. Ranger (file manager), cmus (music player), qutebrowser (web browser, full featured unlike Lynx, which I do still like, but I use eww in place of it most of the time), etc, etc. Tons of stuff that can make your setup far, far less mouse dependent. Starting with learning the terminal, then using a twm is how I got to the point where I am now where all non-necessary mouse functions are replaced by keyboard keys. Just note that it did take about ten years to get here, though that wasn’t me actively searching for ways to do it, more just naturally making my computer work how I wanted it to without the specific end-goal of zero mouse usage.

Edit: Forgot to include that I did most of this before learning Emacs at all. I’ve used nano for most of my time on Linux, only switching to Emacs last August. Only thing I didn’t have before that was cmus. It also works as an email client, but ehh… I don’t feel a strong need to switch away from Thunderbird at this point in time.