I use a 7 plus and my setting and background apps are as before the os11 upgrade. Why should I compensate for an Apple problem?
In all versions, I get lots and lots of battery range. The challenge is if you have brightness set to highest range, when not needed is wasteful. Also, if you have a dozen apps running at the same time or if you let everything track and report your whereabouts. I can run my iPhone 7+ several days without charging, definitely a full day with heavy use. Same with my iPad Pro. Just got to realize the battery is not unlimited. (And if you think the battery is not holding up as you think it should, drop by the Apple store and have them test it. We did this with our older phones, they verified in our case that the batteries were still fine.). Anyway, not defending Apple, but I find the phone has lots of battery and I never face it dying during the day (unless I forget to charge it periodically.)
And by the way, what Apple problem do you suggest for the battery? I sure don’t see one and see no discussion of one anywhere. Maybe you have a defective phone?