You should know the chips are designed to run right past 100c. If they're cool the majority of the time "normal" then those temps aren't a problem. If they're cool 50%+ of the time you'll eventually run into lag and know it's time to shutdown and leave.

They're not designed on plastic. It's a'ok.

You can replace the thermal paste on GPUs quite easily so combined with thermal paste replacement on a CPU you'll know your computer is designed for whatever it pumps out otherwise.

Major heat damage is absolutely obvious. Cards are designed for 2 years on overclock and 5y+ anything otherwise because of moving parts and consistent use. If your CPU/GPU aren't overclocked and you're hitting those temps you're fine.

When you start going near end of 90 start of 100s you know you've got a serious problem and you need to rectify it... but they're nowhere near.