

You didn’t list the hardware or what the temps used to be before this. Assuming it’s a recent increase from sane normals, your best course of action is to move the system, give it a thorough cleaning, and change the thermal interface material. Underclock / undervolt is a temporary solution as inadequate heat dissipation can still occur even if the temps appear normal, degradation will continue.
You won’t brick the computer by moving it and changing the thermal paste. If you’re not confident enough, just watch a video or two online about how to handle the system, I bet there’s videos of your specific hardware out there. You’re more likely to incorrectly configure the hardware via software controls than you are to damage it by swapping the thermal paste.
Yes, look on their website for compatible models, there’s a handful of affordable ones, many which perform better on higher tier connections too. Been using my own modems with Comcast for 25 years.