There are programs (OCTune is one) that let you overclock and otherwise tweak your cards. You can also track what voltage you're consuming, what temperature the card is, how fast the fan(s) are spinning, etc. So it's fairly easy to calculate the efficiency of what you're doing, or step back from the overclocking to increase stability if you get janky behavior with aggressive overclocking, or even underclock it if the heat issue really concerns you.
Also congrats on the 3080FE, I've heard those are really tough to get lately not even including getting gouged on the price by scalpers.