In the case of blue rov’s power module, 25.2V 100A is used, and I would like to know what criteria was selected.
For example, I want to know whether it is based on total power (W) or total current (A).
Also, could the soldering part melt due to overheating of the power sensor module?
The electrical characteristics of your power sensor depend mostly on the output capacity of your power supply. If your battery is 25.2 V then you need a power sensor that can handle at least that amount.
If you’re expecting all 6 thrusters to have full throttle at once then you’ll have peak currents as high as 147 A (plus the current for your other electronics), and you’ll need your power sensor to at least be able to pass through that amount of current, and preferably also measure up to that amount. It may make more sense to determine the current limit based on the capacity of your power supply / battery, because you’ll need to be limiting throttle to within that level anyway (otherwise your control electronics may restart themselves due to under-powering).
You should be ok as long as your power sensor can handle the power supply capacity. For some extra robustness you can make sure it’s rated to a bit above, but if you’re operating outside the capacity of your supply then you likely have bigger issues than not being able to accurately measure exactly how much power you’re using