I agree, I think in the end it just doesn’t matter. I’ve mentioned in other conversations with you the 6s I have on iOS 10. A slightly higher cycle count than OP, 63% health, and battery life is still like-new. So even if you don’t want to replace a battery (which I don’t), it doesn’t make any difference anyway, and I can enjoy all of the battery life of the device, all the time.If I were a light user with a 2015 purchased 6s+ that upgraded to a Pixel 3a XL in 2020, then to an 11 Pro Max in 2021 while KEEPING said 6s+ and using it as a secondary phone that entire time…
…I would not worry about optimising its charging at all. 😉
I think that for the sake of battery conservation it’s much better to charge with a 5w charger and avoid heat, and if you can, don’t update iOS. It’ll be fine for a very long time like that.
For the sake of an example, a family member has an iPhone 8 with 78% health and nearly 2000 cycles on iOS 14 and the device is completely fine, I’ve tested it myself, battery life is great. (Surprisingly, it was forced from iOS 12 into iOS 14 by Apple and it didn’t affect it too much), so if the iOS version is a decent one, you can use it pretty heavily for years and it’ll be fine regardless.