What water profile should be used for a Maibock?

You could look-up the water profile from Einbeck north Germany, where the style originated. You'd get some authenticity points too. The reason they used the malts they did, in many cases, was to help out with controlling the pH of the mash, so by using some of those profiles, you're actually making it harder to convert in the mash. But that 'struggle' might just be what gives the beer it's character.

I've not brewed a maibock, but I've brewed plenty of Munich Helles which the BJCP says the maibock is a stronger version of. Since it's a malt-forward style, mostly on account of the large amount of malt and proportinally less hops.

I would use a neutral profile or one that accentuates the malt, and achieve the hop balance in the quantity of hops used, rather than trying to eek out more hoppiness by adding sulphates. A little carbonate may be helpful, as is typical of Munich water, to help offset the darker munich malt.

The spreadsheet gives color ranges for "yellow" and "amber", so after you put your recipe together you select the color profile. Malty or balanced will depend on the recipe, also. In general, though, I think you could go with either and be OK.