But what exactly is a charge cycle? I mean, the effect on a battery being loaded from 0% to 100% and drained to 0% again is vastly different from a battery being charged from 40% to 50% and being used until 40% ten times in a row.
I plug mine into the charger when I go to bed, and unplug it in the morning when I start my day. I don't have time to think about phone charge levels much beyond that.
I don't know much about Android but assume there must be some way to do similar automations (because I've never seen in any of the Android vs iPhone arguments someone say go with iPhone because of superior automation support).
I recommend going with Matter for the smart plug because if you use the manufacturer's app to control it those often require that you be logged in. The problem with that (beyond any annoyance you might have at needing to make an account to use your device) is that the login might occasionally expire, then your automation breaks.
¹I can't use Apple's charge limit setting because for some reason I can't even guess at when they finally added it to iPadOS they only added it iPads newer than my iPad 10.
It specifically has an option for 80% (const) or an "Adaptive Charge" predictive algorithm that charges to 80% and then only fully charges to 100% right before you typically unplug it from the charger.
Because my experience has been that the cycle count doesn't matter that much as the battery gets old. Old batteries just lose capacity.
So even when you don't use them, you have to babysit lithium-ion batteries. That's why I still love devices with those crappy AA batteries. In general, those have lower capacity, but you can just dump a device into a drawer for 3 years (remember to take the batteries out or use rechargeables) and just put fresh batteries into the device when you need it.
For example, I have those wireless Sennheiser over-ear headphones, which are probably 10+ years old, but they just keep working because they use AAA rechargeables.