Not convinced that my starter needs to peak
So I will try to explain why I think you don't need the exact moment the starter needs to peak and you can use it at almost any time as long as it is really active.
Let's for example take a starter that is really active and you've been feeding it every day.
It's a 1:1:1 of 20g for each ingredient meaning 60g total, and I know by checking it everyday that it needs 6 hours to peak and stays there for 3h before starting to fall at 24-25°C.
Now, let's say I decided to create a new levain from my original active starter, a 1:5:5 to use in my recipe.
Meaning 20g of starter 100g of flour and 100g of water for a total of 220g.
So now I know from my 1:1:1 original starter that the 20g of starter are going to eat the first 40g in 6h (there own peak) and become 60g of levain, so there is 160g of food left for 60g of active levain, now my 60g will eat 120g in 6h and become 180g of levain, so there is 40g of food left after 12h and it's really close to peak now.
Now if I were to take the 220g of starter after 6 hours (way before it peaks), and put it in my recipe, I know that only 60g are going to be active and the rest would be just simple flour and water, that means if I were going for 20% of levain in my recipe, this would make the % way less because only 60g are active, meaning that instead of fermenting faster it will ferment slower, but that doesn't mean my starter is weak and it won't perform well, it just didn't fully transformed, we all know that there are recipe that goes from 5% starter to more than 20%.
To resume it, it's like instead of putting in my recipe my 1:5:5, I took my 1:1:1 at peak and used it, it just the % relative to the dough that changed, you will just need to adjust the recipe accordingly, so that's the hard part (taking into consideration the flour and water left in the starter that didn't transform, if you want the correct percentage you were after).
I could say that you can use your starter at any point during the rise (at least a minimum), but the only difference will be the fermentation time since the active part will be smaller, it doesn't make it stronger or weaker as long as your original starter is fully active, it is just slower.
The only benefice of a 1:5:5 starter is that it gives you some flexibility in your timing since it takes longer to transform.
Now when it start falling I think that's not a problem also, cause that means that the whole starter has transformed and it needs food, but the only down side is that the acid start to form and it damages the dough, as long as it is close to peak I think it's fine.