Question: What are you developing?
With that said, NixOS would probably be fine, if not better than fine. From what I can tell, I don't think Guix would be a good idea - the packages appear out of date, according to their package manager. They're still on Python 3.10.
However, I might recommend Debian Testing to you for your purposes. Most of the time, packages are pretty recent, maybe a few months old at the most (sometimes just a few weeks), but you still get most of the stability of regular Debian. The only asterisk is when the freeze happens. I think apt may have gotten some updates as well.
I've been using it on my desktop PC for over two-and-a-half years. I will say I have grown a bit weary of it, as it gets so many updates and software changes so fast. On my laptop, I went with stable and plan to switch or stable on my desktop once Trixie gets stable.
In brief, Testing isn't bad. I'd almost recommend a development VM.
Before I continue, you should probably specify your budget explicitly.
With that said, almost anything older than a few years should do what you need to just fine. I have a Lenovo Yoga 710 from 2016 that works decent, and had an old Fujitsu Lifebook from 2010 that wasn't too shabby as well. Heck, I once booted Linux off a cheap piano black Toshiba laptop originally made for Vista.
Just choose a random old laptop and you'll most likely be good.