I understand what you're trying to do but for me there isn't a simple answer - much depends on the size of the plants, the size of the containers they're in, and the ambient temperature.
A fully grown tomato plant consumes much more water than a young one, and in warm sunny weather my greenhouse plants need watering every day, but in cooler cloudy conditions perhaps only every 3 days.
Obviously hard to reflect that with an automatic watering system - I think you can only use trial and error to aim for a compromise flow rate which will avoid extremes of over or under watering most of the time.