How would I know how much to invest then?
You invest with what you're comfortable with.
Usually I get x amount of coin per coin but I dont know in this case?

You don't know the price till the end of the crowdsale.
What is the minimal amount and maximum amount someone can invest? self.NVO
There isn't one. I would not suggest investing less than 0.01 BTC though.
Also what determines how many coins a person gets?
Total amount raised / 15 000 000 = price per coin. That will be calculated after the crowdsale has ended.