It runs well. NT4 is my preferred OS for a regular Pentium if it's doing some practical task and not playing games that require a different OS. It's faster than Win98 or 2000 because it uses the classic shell, and it's way more stable than Win9x.
Many years ago I installed NT4 SP6a on my sister's P133 laptop. We maxed out the RAM to I think 80MB. It was fine for basic usage until the internet got all modern and scripty.
More recently, I've installed NT4 SP6a on a P75 laptop which I use for car diagnosis. That machine has less RAM but it's enough for how it's used. It runs smoothly, but I don't do much with that machine.
People I knew always used to say that NT4 "isn't for laptops", but I disagreed and still do. No, it doesn't have many power management features, or maybe none at all, but that's a petty issue compared to stability. Pentium-era laptops were rarely used for games, and if they were then it was games that supported NT4 anyway. I wanted Pentium-era laptops to be reliable workhorses, and NT4 makes them so.
I agree that 32MB RAM is probably the minimum to consider, but preferably more.
I remember a computer lab in school that had NT4 with 24MB RAM, and that made it unusable. The program we were using for that class kept crashing every 5-10 minutes due to lack of RAM. Some students who were dependent on that lab started complaining to the administration because they couldn't get any work done.