2 millimetres length is enough for work. How can I reliably cut them to that length? I am used to lining the finger clipper to my fingernail and sometimes undercutting.
You can cut to any desired length with scissors and with most clippers, experience will make it easier. So try it and keep trying. I often break one nail while at work and need to cut it, and then want to cut the rest to the same length. Each next time it is easier.
But I have noticed that it is easier when you use a file.
And filing your nails has the advantage that you can take off very little and can always keep your nails the length and shape you want them.
Any nail file will work for this, a diamond file is very nice but not needed.
I cut my thumbnail and first two fingernails slightly long (about 1 mm) and the last two nails short (0 mm). After cutting with a nail clipper, I use an emery board (maybe 180 or 200 grit) to file them to be smooth and even (so they don't snag clothes). I find that metal nail files (such as the ones built into fingernail clippers) do not have sufficiently fine crosscuts, so I only use those for emergencies.
To answer your question, using a clipper and emery board makes it easy to cut them so the finished product is the desired length. I leave the nails on the thumb and first two fingers a little long in order to be able to pick up small objects and fit in tight places, using them like small tools. The last two nails are virtually useless for this purpose, so I cut them short so they're not in the way. By the time my three nails are at 2 mm, they're too long and almost like little knives. That's when I cut them back to avoid injury by accidentally grazing myself or others.