Hello Tcbofade!
It's clear you are asking about breakpoints associated with revolving utilization. It's unclear, however, whether you are asking about overall U or per-card U. You talk at least once about overall and at least a couple times about per-card. Can you clarify?
Another thing I am unsure about from your post is whether you are chiefly interested in (a) getting practical guidance on what steps to take (with your cards) to improve your score -- or whether you are more interested in (b) the theoretical question of what breakpoints might exist, purely for the pleasure of knowing about the models for its own sake.
If (a), then the answer is pretty straightforward. Your goal needs to be to pay off all of your cards in entirety, and to do so as quickly as you can. And then moving forward, to pay your cards in full. And finally, when you need to maximize your score for any reason (because you are about to have a really important credit pull, e.g. mortgage pre-approval, etc.) then make sure all CCs except one report $0 with the remaining card having a smallish balance.
That's the practical "what should I do" advice. I hear you that you can't achieve this next month. But knowing what breakpoints might exist doesn't change what the goal should be, which is paying your cards off entirely. (There are several reasons why this is an important goal, of which "what will this do to my current FICO 8" is only one.)
If (b), then we'd need to know more about whether you are talking about per-card or overall. But just as important, you'd need to know that testing what breakpoints might exist and where is difficult, for at least two reasons. The first is that any "test result data" would be true only for the scorecard you happen to be in and for that particular model. The "model" question would probably be limited to FICO 8 classic (rather than the many other flavors and versions) because that is the only model you likely have the ability to pull fresh new score multiple times a month. And for the scorecard question, remember that each model has many scorecards within it (e.g. FICO 8 classic has 12 different scorecards). You might even change to a different scorecard the next month and not know it, which would lead to (possibly) a different set of breakpoints.
The second reason why meaningful testing is hard is that it is very hard to keep ALL scoring model factors unchanged except the one that you are trying to test. For example, even the most rigorous and scientific testing that happens here (and most is far less rigorous) involves pulling your score, making changes, and then pulling it again the following month. But even there, AAoA has changed, age of youngest account has changed, age of oldest account has changed, etc.
None of that means that we don't have some well documented facts about CC balances and how they affect score. For example, a fair guess is that for all FICO models, the "total utilization factor" gives you the same number of points at any point in the range of 1-5%. (Possibly 1-7 or even 1-9%.) We know that the score hit for total U as you move from a total U of 9% to 99% probably involves breakpoints but there are probably very many, so many that it is akin to being gradual. We know that per-card utilization often matters a lot when it is high and probably doesn't matter hardly at all (for most people) when a card is mid-to-low. And we know that you don't get an advantage for having a higher utilization vs. a lower one (unless that is 0% vs. 1%).
Fortunately that knowledge is enough. It's enough because it tells us what to do: pay off our cards (for long range benefit) and how to maximize the score in the short term when we need every extra point.
