Yes, there is an authoritative description that indicates which timers are used for PWM on the Arduino Nano.
In general, the Arduino Nano uses three timers: Timer0, Timer1, and Timer2. Timer0 is used for the delay() function, so it should not be used for anything else. Timer1 is used for the Servo library, so it should not be used for PWM unless you don't plan to use Servo.
Timer2 is used for the Tone() function and for the PWM output on pins 3 and 11. The other PWM outputs on the Nano (pins 5, 6, 9, and 10) are controlled by Timer0 and Timer1, so you can use those timers for PWM if you're not using the Servo library.
If you want to use Timer2 for your own timing functions, you can still use PWM on pins 3 and 11 by using the analogWrite() function. However, you should not use Timer2 for any other purpose while using PWM on those pins.
Overall, it's a good idea to carefully plan your use of timers on the Nano to avoid conflicts between different functions. You can refer to the datasheet for the ATmega328P microcontroller used in the Nano for more detailed information on timer usage.