I've been that month several times.
Rope drop is NEVER essential- even on Easter week.
That said, being in the parks fairly close to rope drop, IS generally a useful time to be in the parks. Alternately, an even better than morning hours are LATE NIGHT hours. In September though rides may well be walk-on much of the day- or near walk-on. It isn't the crowds that are going to limit you - it's the total number of park hours.
We do TEND to use (most of) the peripheral hours most days. For at least the last five years, we almost never aim to ACTUALLY be at the parks at rope drop. At best, we usually arrive at 9:15am - but I know how to time things. If you don't then maybe try to allow more time than you think it will take.
If there is an early morning downpour, or it's very cold- sometimes we opt to go late. On the other hand - rainy days will be less crowded. On the other hand- thunderstorms close half the AK attractions.
In Sept, if youa re sticking only to regualr park hours- then the parks close pretty early. Even with the low crowds, it's not enough park hours for my tastes. If you are thinking you are going to arrive after rope drop, take an afternoon break, then head back to the parks and manage to see everything - that is not going to happen.
Many nights, MK closes by 7pm. HS closes by 8pm. That doesn't give you much for evening hours unless you want to pay extra for the Halloween party at MK.
Than again....you dont HAVE to spend all your waking hours in the parks....WDW does have quite a few non-park activites. Eating is one.
In September, we find it helpful to eat most dinners after 7pm. On you AK day, you can eat after 5pm. So that's another factor. We also don't eat TS lunches or breakfasts. So you can get the most out of your park hours if you aren't eating - especially long TS meals. Another consideration is to maybe time lunch to coincide with any afternoon thunderstorms. (usually half an hour between 3-5pm)
I can't be up early enough to be at MK for a breakfast that will be OVER before 9am. If I am in MK at 9am - I'm taking advantage of that time to be on attractions, not eating. Before
DDP, we sometimes did one late TS breakfast at CP. If we do a late buffet breakfast, then we can skip lunch.
That said, we stopped going in September for several reasons. Limited park hours is one. If you dont do RD, then it is helpful to use as many of the park hours as you can - esp evening EMH's.