Watanabe Type R Fitment
 

What would the look be like for a pair of 4x100 16x8 +6 Watanabe type R wheels on a stock FC? How much or little would they stick out in the front and rear?

Just using the wheel calculator, stock FC with 15x6 40mm:
16x8 6mm-Inner clearance 9mm (.354") more and outer position would move out 59mm ( 2.32")

I apologize I am not the most knowledgeable when it comes to wheels and things of that nature. This will probably sound stupid, but would you be able to dumb that down for me a little bit? It would be much appreciated.

He's saying the outside of the wheels will stick out 2.32" further than stock.
I'd guess the fronts will stick out about 1" past the fender and rears will be close to flush.

4x100 won't fit an FC without some kind of adapter, FC is either 4x114.3 or 5x114.3

adapters are possible, they run about $100 (probably $150+ these days) however you do need to take the thickness into account, they move the wheels out