Consider that the energy output of a 12-gauge shotgun is approximately 4500 Newton-meters and, from personal experience, can rotate a first-gen iPad at an extrapolated 240 rpm (extrapolated as this proved difficult to sustain). That gives us an equivalent of 113 kW! A modern ipad would only need about 13 kW to charge in one second.
So, one shotgun shell could easily charge yours and 7 of your friends ipads instantaneously, although the results are difficult to appreciate.
Battery degradation is ridiculously unpredictable. I've seen 100 cycle batteries at 75% and 2500 cycle batteries over 90%. I only dealt with like 5 MacBook models
Depending on what battery protection modes are in play, many have smart charging or other features designed to prolong life. Also a fair few batteries come out with greater than design capacity from the factory. It's called a design capacity and not an absolute capacity for a reason. A phone battery that left the factory at 110% could conceivably still be at or above 100%.
Fyi it's not overnight charging that's the issue either, it's charging to 100%. What one device consider 100% varies and devices will essentially lie to you about it. 4.2V is normally considered 100% full for Lithium Cobalt Oxide batteries yet some devices push higher than this while others skirt under to pad capacity and cycle life respectively. It's about tradeoffs.