PWM signals averaged or not
Many of your questions can be answered here. Where it says that the output of a PWM is dependent on the inverse of the period of the PWM signal times the integration from time zero to time 1-period of the PWM function:



This is explained in this part the above web page. Bottom line, the output of a PWM signal is the duty cycle.

The Arduino analogWrite() library call accepts a value of 2^8 or 0 to 255.  The 100% duty cycle is represented by 255 and 0% duty cycle is represented by 0.  This is talked about here.   So, no, you can't use the formal value you pass to this Arduino library function as the voltage.  Do some research, but I believe the voltage is more along the lines (for a 5 volt power supply) approximately five volts times the value divided by the maximum value.