Since most of my pizza doughs use small amounts of yeast and since I control temperatures of everything as best I can, I rarely have a problem with doughs overfermenting. After years of using this approach, I think I developed a sixth sense, largely based on technical factors but including some intuition, for when a dough should be ready to use. In a sense, I "program" the dough to be ready when I want to use it. But, on occasion, a dough ball will have its own mind and want to do its own thing and can be ready sooner than I planned. Usually it is temperature related and where I perhaps didn't do a good enough job controlling the finished dough temperature. However, since I use the poppyseed method most of the time, at least until I learn the dough's behavior pattern, things don't get out of control. So, once a dough doubles in volume, I pay close attention and I observe the degree of fermentation as evidenced by the amount of fermentation bubbles that I can see in my glass or plastic container at the sides and bottom.
I also observe the top of the dough to see if it is firm. If it is firm, I usually don't worry about the degree of fermentation of the dough. I also discovered that bubbles can form at the top of the dough yet the dough is not overfermented. If the top of the dough is firm and not billowy or soft, I just pinch the bubbles shut. If the top of the dough is soft and there is a profusion of fermentation bubbles, then I use the dough. You can see examples of bubbles in doughs that were not overfermented at Reply 3 at http://www.pizzamaking.com/forum/index.php/topic,2238.msg19652.html#msg19652
and at Reply 29 at http://www.pizzamaking.com/forum/index.php/topic,3985.msg36081.html#msg36081
. These were doughs leavened with commercial yeast, not a natural starter or preferment. These days I am more lilely to use glass or plastic storage containers to allow me to better see what is happening at the sides or bottoms of the dough balls.
In terms of sourdough flavor, I personally do not like crusts that have a flavor such as one would get in a classic San Francisco sourdough bread. I have never gotten that type of sourness using any of my natural starters/preferments. The flavors have always been complex but not sour.
What I was interested most in your experiment is whether the large amount of Ischia poolish starter you used would produce too much acid that might affect the strength of the gluten structure in a way as to make the dough overly elastic and difficult to open and stretch, which would not be desirable for use at market if you ever took it that far. That might be more common with a poolish that is leavened with commercial yeast and is given a chance to produce a lot of acid in the final dough but it may be that that isn't an issue with a natural starter or maybe your fermentation protocol, including a period of cold fermentation that slowed things down, did not reach the point of producing an overly elastic dough.
My practice when embarking on a dough project such as yours is to frame the issue by working both extremes of the exercise so that I get a clearer perspective of what the parameters are. For example, I might first use a very small amount of starter and then a very large amount of starter while keeping everthing else exactly the same as much as possible. Otherwise, I won't do the experiment. Then, based on the results, including personal preferences that emerge from the exercise, I fill in the gaps with other experiments. Often the results suggest the next experiments to conduct. In your case, you have done two such experiments at somewhat opposite ends, even if the latest one was by accident, so you may already have decided in which direction you want to take your next experiment.