Are we allowed to use longer wires than the ones that come in the kit so the motor controllers can reach each other?
The quick answer is no.
This is not the official FIRST Forum and to get a truly binding and correct answer you need to search the official Q&A first. If you can not find an answer to your question there then you should post you question and wait for an official answer.
Yes (see Q&A). The wire must be the same type and guage as the kit.
This is essentially #20 red and black wire.
You must use complete lengths (no soldering or splices)