ripgrep is an excellent grep replacement to check out. wild how much faster it runs. +1 on the eza (other poster said exa but that's abandonware forked to eza)

check out deploy-rs and ragenix once you've replaced your current media server with a NixOS one. They make it much easier to apply configuration changes and to handle secrets if you need em for configs. +1 on start using flakes ASAP if you're not already (pretty sure both these tools only work with flakes), Xe Iaso's got a bunch of good blog posts about em if those are your jam.

I am currently playing around with it in a vm until the config is to my liking.

this is how I got NixOS to click for me, 10/10 highly recommend. even if it doesn't stick this time keep your config in source control somewhere so you can revisit it.

Any reason to use an alternative to bash?

gonna strongly disagree with one of the other posters in here that you should use POSIX-compliant shells because they're more portable, for a few reasons:

1. if you're using the shell on a server or someone else's workstation to do more than run a handful of diagnostic binaries you're already wasting your time, and even then finding a quick one-liner in stack overflow to do some annoying repetitive task like filesystem cleanup or the like will be trivial. goes double for nixos where the likelihood you're doing anything once shelled in besides editing a config or running a diagnostic becomes even more unlikely
2. speaking of, since you use nixos, you can trivially have your preferred shell environment available on any server you're running for yourself
3. modern structured data pipeline-based shells (PowerShell, elvish, nushell, etc.) are far more ergonomic for both interactive and scripted usage

I wrote a little bit more about how modern structured data shells have been a more ergonomic option for like two decades now in a dunk tank post a few weeks back so I'll just link that instead of elaborating.

even if you find you prefer flat text pipelines, zsh and fish are fine (and were preferable for me for interactive use before I started using pwsh and then elvish) and you'll still wind up writing bash scripts anyway. or at least when I used those shells I don't think I once wrote a script that targeted them instead of bash. also #! /usr/bin/env sh is fine, you should hopefully be well aware when you write scripts that have a chance of running on a system that has a weird shell symlinked to sh.