How to fix overheating GPU?

low end cards that can be overclocked to perform as well as your low end 1070 for a fraction of the cost

underclock
replace thermal paste

Same card, idles at 45, peaks at 70 and gets quite loud.

can't suggest much except give everything a good clean and invest in decent thermal grease

but they will need high end cooling

well maybe you should start telling us about your buttplug collection.

clock it down
water cooler
dont buy those oven vent cards

Unscrew the whole GPU cover plate and clear dust then.

Change the thermal paste, you dimwit.

reapply thermal paste with arctic mx5

You need to fully disassemble the cooling, clean the heat-sink, and re-thermal paste the GPU.