Unstable clock speeds and power have zero relationship when you design the circuit. You can easily design something with a few transistors that will violate set

Unstable clock speeds and power have zero relationship when you design the circuit. You can easily design something with a few transistors that will violate setup and hold times at 1-10mhz, which you can get out of a very low power crystal. You could even use an off the shelf mcu with a low nominal clock speed and just point a fast resonator at it. You can even make things unstable by giving it too slow of a clock speed. Most semiconductors don't want to hold a charge difference for very long.