I looked at several datasheets, 1 place claims 1.5 watts output.
There is only one datasheet, not several. The LM386 was made by National Semi who was purchased a few years ago by Texas Instruments.
The datasheet shows 0.7W into 8 ohms when the supply is 9V and the clipping distortion is horrible at 10%. A graph shows that clipping begins at 6Vp-p which is 0.56W and some calculations show that there is low distortion at 0.45W and at lower power.
The datasheet shows 1W into a 16 ohm speaker that is not used today and a 12V supply. A graph shows a small increase in output power with an 8 ohm speaker with a 12V supply but much more heating.
Most circuits that shows IC pin locations with parts shows 10K variable resistor pin 3 with no capacitor but some show .1 uF capacitor.
If the signal source has DC then the input capacitor blocks the DC from upsetting the volume control and the IC. If you do not want bass then use 0.1uF as I show above but the calculation is simple for the input and output capacitor values for the lowest frequency you want.
Most datasheets show 10K resistor in series with .05uf capacitor on pin 5, only one circuit shows 10 ohm resistor.
The single datasheet shows that the Zobel network at the output is 0.05uF in series with 10 ohms.
Output capacitor is not the same for pin 5 on all datasheets either. It is hard to know what is correct datasheets are not all the same.
The value of the output capacitor is simply calculated with the speaker impedance for the lowest frequency you want because the capacitor and its load are a highpass filter.
WHY such a variation in parts values on datasheets?
The input and output capacitor values are different because some people want good bass and other people have tiny speakers that cannot produce any bass or have a telephone input signal that has no bass.
I expect Google search for LM386 circuits to be different most of those circuits don't work. There is usually good information in, TTL books, CMOS books, Transistor Logic books, Semiconductor books.
Some websites post errors but the datasheet and education are always correct.
Is there a chart somewhere that shows Hz for each capacitor value?
When the level is reduced -3dB then everybody notices the small reduction in level. -3dB is half the power or is 0.707 times the voltage or current.
The -3dB cutoff frequency calculation involves the capacitor value, the load impedance and pi. The calculation for the capacitor value is 1 divided by (2 x pi x f x R). For example, a 91Hz cutoff happens when the speaker is 8 ohms and the capacitor is 220uF.