For my first project, I am building an adapter to use a USB game controller (a Switch Pro Controller in this case) with a Gamecube console.
I got everything working using the USBHost_t36 library and with the Teensy connected to my laptop.

Now, since this adapter is meant to be used on the go, I would like to use the Gamecube cable to power the Teensy from the console instead of my laptop USB port.

The Gamecube console provides these pins:
- 3.3v data (used to communicate with the console both ways)
- 3.3v GND
- 3.3v power
- 5v GND
- 5v power

I am already using the 3.3v data and 3.3v GND pins to communicate with the console.

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Here come the newbie questions!
1) Are the pins provided by the console enough to power the Teensy 3.6 (96Mhz) + USB host port/guest device?
2) Is it safe for me to connect the 5v pin to Vin and 5v GND to the Teensy, even though I already have the 3.3v data and 3.3v GND connected?
3) I read that it is not safe to have both USB and external power at the same time, how can I work around this on the Teensy 3.6?

Thank you for reading and for your help!