What value resistor to add, so my motor provides the correct amount of power?
The motor controller in your drone doesn't use resistance to control motor RPM. Instead, it uses a PWM chop to vary the duty cycle and thus the delivered power. Duty cycle has roughly a linear relationship to power delivered to the load, which will have some not-linear relationship to RPM.

An inexpensive bench supply with variable voltage and current is a way to model delivered power. In this way you can directly characterize motor input power vs. RPM, a somewhat useful figure.

You have two ways to do this.


Vary the voltage, observe the current and RPM
Vary the current, observe the voltage and RPM


Either one will give you W vs. RPM.