I have a 100% whole wheat starter. In the morning, i'd like to throw away half and feed it AP flour. 4 hours later it's going into a dough, and be bulk fermented for at least 24 hours in the fridge. Then it's going into the oven. Will I have less of an open crumb if I do this? The main dough is also made with AP flour.
I've found that my starter really likes rye. So I feed it a mix of rye and white. I make a levain and I normally will just use whatever is in the bread. So if I make a loaf with 60% WW and 40% white, then that's what I make a levain with, changing the flour doesn't affect it. That being said...
I normally don't go under 40% Whole grain in my starter because I like the way it consistently rises. When I've switched to white flour I don't get the same consistency. Plus if your starter is used to whole grains, it may take some time for your starter to adjust to no whole grains. So there will be a period where it isn't as strong. That being said, tons of people use a white starter. Try keeping a little whole grain, for something for consistent.