The external header description is a little unclear for me:

• What does 2 - PWR_EN mean?
• What is the difference between 3 - 3V3_Sensors and 4 - 3V3_Pymodule?
• I can control the lopy4 rgb led over 5 - EXT_IO0 (RGB_LED) from an enxternal controller? Or what does rgb_led mean?
• If I want 5V from pytrack+lopy4 combo I can't do it over the external header? Like configurate G15 to OUTPUT.
• What does PIC_RC0 and PIC_RC1 means?

+Bonus: Can I use 2 18650 batteries to power the sytem? I should use them in paralel if I am right. Can I use the jst connector or hook it somewhere else?

Thank you in advance! :)

• 2 PWR_EN: it's connected to P3 (same)
• 3 3V3_Pymodule: 3v3 coming from the board
• 4 3V3_Sensors: 3v3 going to the sensors on Pytrack.
• 5 PIC_RC0 is toggling the bootloader mode and connected to P2 RGB_LED
• Yes, you can control the LoPy 4 RGB Led over 5

I assume you can, as long as it's within the specifications of the module (you can find the datasheets on our docs) . Note that we don't take responsibility for damage caused by 3rd party parts.

• 2 PWR_EN: it's connected to P3 (same) - Still don't get it what can I use it for :(
• 3 3V3_Pymodule: 3v3 coming from the board - So, this is the port where I can power some external moduls? like sensors and such
• 4 3V3_Sensors: 3v3 going to the sensors on Pytrack. - Still don't get it what can I use it for, If the pytrack is connected to lopy4, and a the lopy4 is on (powered through pytrack via jst or usb, than why would I need to power them externaly?
• 5 PIC_RC0 is toggling the bootloader mode and connected to P2 RGB_LED
  Yes, you can control the LoPy 4 RGB Led over 5 - How? Like I took an other devboard (esp32 or such) and controll the led bypassing the lopy4? What would be the benefit of that?
  I ordered a this 5000mah Li-ion battery.

3V3_Pymodule is powered when the module (LoPy 4, FiPy, etc.) is powered.

3V3_Sensors is powered when the sensors on the Pytrack (GPS, accelerometer, etc.) are powered.

IIRC they are controlled by separate pins on the PIC and you can choose to power the sensors or not (see the Pytrack libraries for details).

The right API is: https://docs.pycom.io/pytrackpysense/apireference/sleep.html

Also, it's 3V3_Pymodule which is always shut off when the Pytrack/Pysense is sent to deep sleep.

3V3_Sensors isn't. Actually, I don't remember if there's a really a condition (such as asking for the GPS or accelerometer to be kept on) or if it's alway kept on.

If you use Pytrack/Pysense-controlled sleep, the PIC will power down completely the FiPy (it's not sleeping, it's completely off), stop USB, etc, and go to sleep. On a Pytrack you can choose to power down the GPS as well. Don't remember about the other sensors on the board. 3V3_Pymodule will be shut down. 3V3_Sensors can be kept on, though I don't remember if it's always on or if there's an option to shut it down as well.

If you use machine.deepsleep, the FiPy will go to sleep, but I believe the Pytrack/Pysense will continue to work as usual, with everything powered. You probably need to take a few steps to reduce its power draw. Don't think there's anything in the libraries for that, you'll probably have to talk to the PIC and/or sensors directly, and I'm not sure there's a way to make the PIC go to sleep without shutting down the FiPy (though I don't know how much the PIC itself draws).