So,
To measure the 4700uF cap you need to select 100Hz but ESR will then show zero.
Yes, because "most" switching caps ESR are "rated and measured" at 100KHz, not at 100Hz, its a common industry practice.
Then you select Rs mode and select 1kHz for an ESR value?
More likely at 100KHz, not at 1KHz as most capacitors are made and measured at this frequency by the manufacturers.
The point here is to see if the capacitor is "STILL" in spec or at least near as new from factory, don't you agree ?
Just download few cap datasheets to get the feel and clue.
Auto range is fairly useless?
No, actually pretty handy for components that we don't have doubt, just to verify its value.
The Auto has limitation, read the manual.
Say you have a cap that shorted inside, the auto definitely can not tell if its a cap or an inductor, or an inductor that it's coil is disconnected in the middle and mis-indentified as a cap, is this making any sense to you ?
If that is the case, then setting to manual to clear things out.
Remember, having both AUTO and MANUAL means we are in full control on what we measure, instead of leaving that dumb thing to decide as they're NOT smart enough.
Do the other meters, like the Atlas ESR70 simply do this in one step?
Does the MESR-100 auto range for ESR even at the higher values?
Never used those, but for me at least, an ESR meter is not in the league compared to a fully LCR meter as you own.
Some crappy ESR meter even can not differentiate between a shorted cap vs a low ESR cap.