If I remove absolutely all configuration from router CPU Load is 8% constantly? I am not complaining because on maximum my router is 35-45% CPU usage but as I think, should be there 0 or 1% CPU usage?

Look at the profiler tool. You will see SPI consumes the 8% CPU.

That is the LCD Touchscreen. Turn it off, and the router will be at 0%.

Yes, You are right. LCD Touchscreen consume 8%.
TY