They are right when they say that about the water being good to drink. Adjusting water chemistry can help to optimize your brews. If you are using an all grain method, then alkalinity is the key component to watch. Roasted malts lower pH, so you will need the extra alkalinity to counter that. Conversely, light grain bills will not mash as efficiently when the alkalinity is too high. Increasing your sulfate relative to chloride will accentuate hops, while higher chloride in proportion to sulfate will accentuate malt flavors. For the IPA, I would go with the Buton On Trent profile, but the sulfate doesn't really need to be so high, 500 ppm should really be plenty. A Dublin water profile is good for stouts as it is relatively soft but high in alkalinity, which would be good for countering the acidic roasted malts. If you can get the sodium, magnesium, and calcium levels for your water that would help, but isn't necessary. If you are extract brewing, I would just really focus on the Cl to SO4 ratio though.