Happy to share (I don’t get the opportunity very often to just talk about the classical guitar itself!).

You don’t need a tension tool or anything; you’d wind the string like normal up to pitch. If you’re new to restringing them, I’d suggest using a tuner that displays the frequency in hertz so you don’t over-tighten. I eventually got to a point where I can hear/feel when it’s close to pitch.

Some caveats though: Nylon strings stretch. So it typically takes awhile for them to settle and stay in tune. I learned in college that tuning them up a full step would stretch them enough to set overnight as opposed to a week. Also, with high tension strings specifically, you have to wind the string a lot for it to reach the correct tension, so the only tool I’d recommend is a string winder (but definitely not an automatic one).

Because the strings are tied off on both ends, they will slip out if the knots are tied in the wrong direction or without enough wraps on the pegs or the wrong knot on the bridge. At higher tension, they slip with much more gusto.

In my experience, steel/electric strings break more often. I never had classical strings break until I started using a specific brand (Hannabach). Apparently this brand is notorious for shitty D strings, which is exactly which one broke repeatedly for me. Luckily, for most classical sets you can buy individual strings, so for every set I would buy, I’d get a redundant D string - and I would always end up using it. Changed brands and no more broken strings.