In my experience, the general trend is that classical guitarists prefer to hear a warmer tone, so make sure you're not constantly close to the bridge. Here is a link to a video of a masterclass where David Russell specifically talks about this, and I think he can explain it better than me.
Basically, having your hand over the edge of the soundhole (closest to the bridge) is the general "neutral" position that players usually assume most of the time. However, this neutral position of course also depends on many factors such as nail length, right hand angle, and the guitar you are using. But I would say a good starting point is the one mentioned above.
Don't forget that for optimal expression and variety in tonal quality, you can feel free to move your right hand around while playing pieces. A good example of this variety in tone and expression would be Julian Bream's playing. Adam Holzman noted in a masterclass I observed that you don't have to have perfectly beautiful tone all the time; deviating to a "harsher" tone at times can make your playing more expressive.
Segovia on timbre: https://youtu.be/DJrEl4Nsmsg