There is an lsd for our cars. The mk6 Wavetrac lsd works in mk7. This is based on what I've read, so would definitely confirm.
That being said, no reason not to g 225-245, with 235 being a happy medium. 235 tend to be harder to find and slightly more expensive than other 2 sizes.
I think 300hp is perfectly reasonable in this car. By no means overwhelms wider tires.
I'm just APR stage 1 (never dynoed but probably around 240) and rarely lose traction in 1st whereas with stock tires, 2nd would be spinning.
It's just night and day from stock and that's a far cry from these guys with ~300.
You will love it. Especially only 2 lane roads where passing areas are few.