Sorry for the late reply.
Both sRGB and Rec709 have the same gamut.
The issue with the MBP is that "Display" settings only allows 1.8 or 2.2 gamma, while Rec709 is actually 2.4 to be precise.
This is something you could compensate by creating your own LUT in Scratch and using it as a display LUT.
Keep in mind that the Player/Settings/Monitor colorspace will only apply on your laptop display and won't have any effect on the exported sequences.