You have two issues here.
1) Do NOT put you own LUTs/Look files into the Program files for PrPro or Me. It causes issues. They have a place now for the 12.x builds of PrPro 2018 ... as shown in the table below. Add the Technical and Creative folders in that location, and put your LUTs/Looks in there. They will show up in the browsing of the Basic tab (Tech folder) and Creative tab (Creative folder) and will be used by both PrPro & Me.
2) QuickTime player is not color managed or even color aware. It is oft referred to as color stupid. PrPro is assuming Rec709/sRGB for color space for the monitor. Your computer is clearly not a fully managed setup. VLC and Potplayer will see that a PrPro export is Rec709/sRGB and show it accordingly. Qt player ... will not.
Next ... the only browser that is color aware is Firefox. Neither Chrome nor Safari give a rip about color spaces, standards, anything. Watching the export in a non-managed computer using a non-managed app like Chrome or Safari can give you anything from over-saturated or contrast to low-contrast/low-saturation.
Last ... the only way you can work sanely is to work with a setup that is color managed, monitor calibrated to Rec709/sRGB, OS set to work with that, and test by putting the material on a good quality well-setup TV (a rare bird, actually) or by finding some nice local broadcast person willing to check a short file from you on their QC gear.
Work so the material is within bounds for blacks/whites/saturation excursions on the scopes in Lumetri. Test a project by re-importing into PrPro.
And when you send it off into The Wild, understand you no longer have any control whatever. NO SCREEN IN THE WORLD will ever show exactly what your screen showed your. It can't. Not even colorists with many thousands of dollars in gear & calibration can make two screens identical.
Throw in various devices, screen types, viewing situation, OS settings, apps ... you have no control whatever.
All you can do is make your stuff to pro spec standards. That way, no matter how it looks on any other screen, it will look as pro material does on that screen.
And if you're on a Mac with a P3 wide-gamut monitor, Heaven help you. Every size of those has a different color space/profile built into it. What a joy.