Headroom for Mastering (peak level)

Headroom for Mastering (peak level)

Any maximum peak level reasonably below 0 dBFS is absolutely fine.

Just make sure to avoid clipping the stereo output.
If you need to put a limiter on the master, in order to prevent clipping, consider alternatively to lower the master fader itself until the peaks are gone (floating point architecture will prevent internal clipping in the DAW so you only need to worry about the output fader).
***Floating point architecture will not prevent plug ins misbehaving if the peak values are insanely abused so please be cautious and use sane levels throughout your mixing sessions.