Plugging it in usually boosts default CPU power plan performance and makes the CPU fully available for whatever program or app is trying to use it full bore.

Try this. Open Task Manager processes tab on battery alone. Then plug the charger in to try to identify which process(es) is causing it. Also try turning on NitroSense coolboost. CPU fan speed should increase to over 5000rpm at those temps.

>>>Like is it normal for CPU usage to be at 2% and for CPU temps to be 65C?>>>

No. Abnormal. Should be mid-50s or less at idle usage. This model might be liquid-cooled. When you re-pasted, did you notice if the tubes from the fan compartments to the CPU & GPU were sealed? There also would've been heat exchangers in the fan compartment if sealed.

Two types of cooling.

The old type is simple air cooling. Cool outside air gets sucked in by the fans. Then pushed through the tubes and exiting directly over the CPU and GPU.

The newer type is liquid-cooled. The tubes are sealed with a coolant inside. Convective flow carries heated CPU & GPU coolant to the fan compartment where heat exchangers (similar to CPU/GPU heatsinks only in the fan compartment) cool it down and returns flow in a convection loop back to the CPU & GPU heatsinks.

I can't tell from your photo or the specsheet photo or the part nos if they are open air tubes or sealed tubes. If they're open air, they might be clogged with dust bunnies that can be vacuumed or blown out. However if they're sealed tubes, they might have developed a coolant leak from vibrations or mechanical stress during re-pasting --- requiring replacement.