If a process is still using too much CPU, try updating your drivers. Drivers are programs that control particular devices connected to your motherboard. Updating your drivers may eliminate compatibility issues or bugs that cause increased CPU usage. Open the Start menu, then Settings.

Is it bad if CPU usage is high?

For an average PC, unless you're doing video encoding, Photoshop editing, 3D modelling or benchmarking your CPU, then 100% CPU usage for longer than a few seconds IS bad. It will increase the CPU temps quickly and your system may freeze.

Is 70% CPU usage high?

It is normal for it to be high because the processor is not doing much at the moment. So, if your System Idle process is using 60% - 70% of your CPU, it means you're actually using 40% - 30% of it. No the System Idle Process is only using 20-30% when running no or very few programs.