When I was setting up my Fiesta to tow, I got a lot of help from this publication: https://webcontent.goodsam.com/motor...inghyGuide.pdf
I suggest you start there, and read other threads on this forum that may answer some of your questions.
I installed the BlueOx baseplate as it was the better looking system when the tow bar is not in use. Not a big fan of BlueOx company as I wrote to them about a design flaw/safety concern and they didn’t even reply.
There are many brake systems, but I recall the BrakeBuddy would not fit right in the Fiesta. I went with RViBrake3 but there could be as good or perhaps even better brake choices. Yes, you need an auxiliary brake system.
I built all my own wiring. I used diodes to tap into the car’s lights. I did the whole flat tow install myself; no way would I let someone else hack up the car.