For a small experiment I decided to use 3 different types of flour as the preferment for Alton Brown's Basic Bread recipe. From left to right in the pics we have white, wheat and rye flour used. In the top pic are 3 preferments made from 5 ounces of whole wheat, 2 teaspoons sugar, 1/4 teaspoon instant yeast and 10 oz water. I let them proof at room temp overnight, and you can see how the yeast fed more on the wheat and especially the rye.
After an overnight proof I used high gluten flour (the recipe calls for 11 oz, but I used 10 because it gets a bit gummy with that much flour after an overnight proof) and 2 teaspoons kosher salt. Proof about 2 hours, shape and proof another hour before baking at 400 degrees for 35 minutes.
The overnight room temp proofing of the preferment makes for a stronger flavor than an overnight or multi day fridge proofing, which I'll do in a side by side experiment later. The dough makes an excellent small loaf that weighs about a pound and a half, and fits into a 1 pound loaf pan (far as I can figure it's called that because it fits a loaf made with one pound of flour and doesn't count the liquid content.)
Today I made some grilled cheese out of the bread, with excellent results.