Do you have to sync it to the Switch every time you power on the console? You have to with the retro receivers which made me go back to a regular wired controller.
Yes, but it's simple. Press and hold start + Y for 3 seconds, and then it syncs. You have to pair it once, and after that, you just go into controller->change grip/order and sync it before starting the game. It charges off a standard phone wall plug w/ USB port too, which is nice.
The pad hack was as simple as they come. Scrape down the the contact points to expose metal, solder wires to the metal, connect the wires to buttons/joystick.
I wasn't aware there is a wired controller for the Switch, but admittedly I didn't look very far. When I learned the 8bitdo controllers were made Switch compatible, and they were more affordable than the pro pad, I went that direction and with the least expensive option with 6 buttons.
Pics of the innards of the stick: