The wet ingredients will vary from recipe to recipe. That is 1/2 cup of fully active starter, water, milk, eggs and honey.
There is very little sourdough taste in these as opposed to when I make bread, that is just due to the ferment/rising time.
Here is how you know when your starter is active…let's say you have 2 cups of unfed starter in a Cambro, feed it 1/2 cup of flour and a similar amout of water. When the starter rises a few inches in the Cambro it is becoming active. For me it has been trial and error when the starter is most active. The starter after it is fed will rise, then deflate again…you ideally want to use it when it is at it's peak.
I may be off a little on my methods, but from what I have read, I think it is correct.
As far as deconstructing a recipe and substituting the starter for flour and water, I have not done that yet. From what I read, you always do it by weight and not volume as weight is supposed to be more accurate.
To simplify it, it a recipe calls for 100 grams of flour, and 100 grams of water, you can replace that with 75 grams of flour, and 75 grams of water, and 50 grams of your starter. Weight is still 200 grams in each instance, but in the second example 50 grams of starter theoretically gives you 25 grams each of flour and water.
Hope that answers a few of your questions.