MacBook Air 2020 cpu sits at 100 degrees Celsius?

While lower temperatures are much better for the longevity of electronics you are still running the CPU within its normal operating parameters (barely). I'm sure it does lessen the overall life of the system to some extent.

You should post the EtreCheck report to rule out any possible software issues that may be causing the CPU to have higher utilization.

The 2018+ MBAirs have an extremely poor cooling system since the heatsink has no heatpipe going to the fan for cooling so this laptop will run much hotter than other Macs.

Once the CPU temps go over a certain threshold (somewhere just above 100C) the CPU will throttle itself if the fan is running at its maximum 8,000 rpm in order to lower temperatures so the CPU doesn't overheat. The CPU speed will automatically increase once the CPU core temperature cools a bit.

To check for other possible software issues that may be working the laptop harder than it needs to run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper.