That's what I do too.
I do think i7-8750H is somewhat an overkill for most of the tasks including gaming, turbo boost is really not necessary.
I underclock to 2.0 GHz by reducing multiplier and everything running perfectly fine, temperature even keeping at 60°C while gaming.
And.. undervolt 0.175V is working for me, it's been running for days (but of course it would be different for everyone).
However, more than -0.2V would most likely fail