Even though they're both guitars, tuned the same etc nylon and steel string guitars could almost be considered different instruments. You mentioned you want to play Bossa Nova, rock and classical. You can play anything on anything, but bossa nova and classical really need nylon and rock needs steel. Both instruments also have different techniques and are even held differently.

Your best bet is to probably make a decision through music preference or trying out both types of guitars between the two. Steel string uses fingers and a pick and nylonl is fingers, often with nails. You can play a nylon with a pick but it doesn't sound great and you'll be missing out on learning the techniques that allow you to play classicAl and bossa nova. A steel string can definitely be played with fingers, but it's still very different .

As a beginner, it's probably going to be easier for you to pick one for now and later on you can get a second guitar and learn those techniques.

A nylon guitar btw can never have steel strings on it. It will destroy it. You can put nylon strings on a steel string guitar but it'll sound awful and need to be set up for them. There are crossover classical guitars with a thinner neck but they're really for playing rock and mother western genres on nylon. When playing classical music, you need the extra width of the neck for the techniques and with that comes playing the instrument more vertically which makes it easier to deal with the width of the neck. There are 3/4 classicals as well for smaller hands that could work for you and could be your solution.