I would recommend a fermentation temperature of 30°C (86°F) if you're trying to get a good balance of acids, but if you're interested in more lactic than acetic, try cooler temperatures for longer periods, and increase the maltose in your dough. If you're interested in more acetic than lactic, aerate the dough more, ferment at temperatures greater than 30°C, and use less (or no) extra maltose. Just as one would expect based on organic chemistry, when oxygen is aplenty, alcohol is oxidized to acetic acid to provide additional energy for the yeast. Lactic acid levels are not affected by the amount of oxygen in the dough to the same degree.
You could also just do what I do from time to time: add lactic or malic acid. If you want to get that sour flavor the old-fashion way, you just have to be patient with your starter.
Any kind of flour or additive that supplies extra micro-nutrients will make a difference. If you plan to create the sour flavor through your starter, I would recommend using something like molasses and/or malt syrup to supply the nutrients though. The added fat in whole grain flour will oxidize over that longer period of time, depriving the yeast of that oxygen. If it's just going to be a preferment, whole grain flour is fine for adding extra micro-nutrients.