As far as using a 20ft USB cable you should be ok.
We usually will use a booster ( power it with additional 5v) after 25 ft just as a precaution but I have run a 50ft USB cable unpowered previously and it was fine.
We usually will use a booster ( power it with additional 5v) after 25 ft just as a precaution but I have run a 50ft USB cable unpowered previously and it was fine.