When you render each track separately, the master fx will not be applied, so the volume of each track’s .wav file will be whatever volume that track is before it reaches the master. If your tracks are loud as hell before they reach the master track, then they will also be loud as hell (and probably clipping) when you render them separately.
To get a better idea of what each track might sound like when rendered separately, you should disable the maximizer on the master track.
You could possibly try to put an individual maximizer on each track in this case, to help keep the levels under 0dB.
If your track headroom (in Song Settings) is -6dB, then your rendered tracks will be at a base level of -6dB.
It’s important to understand that we do not perform any normalisation here. So if you’re still pushing your track level way into the red, then the -6dB headroom isn’t going to be much help, and you will still get a clipped render.
audible in ordinary players or in Renoise as well? Not all players use the overhead information saved with a 32-bit wav file.
If you export to 16 bit rather than 32 bit for example, you would not even have that overhead data saved so the result will distort everywhere.