Okay so, I am doing a very basic circuit to be honest but I will use INA226 (a power sensor) which communicate with I2C so SDA SCL pins (A4, A5) I also need to have a PWM output to drive a logic mosfet (I am planning to drive it directly from the D9 pin since it is a low power mosfet) around 20 kHz (there is no specific requirement). I am afraid that playing with timer1 might (I have no idea) create problems with INA226.