@cleeds You note: "Of course, the overhang will remain constant if you are able to precisely adjust arm height to compensate for various thicknesses of LPs. But if you are adjusting VTA by ear on the fly, what determines to your ear that you've reached the ideal arm height?"
I know when I hear it and it is clearly audible, even to the untrained ear. To paraphrase Bill Nelson, it "makes the music magic, makes the strings ring like bells in the night." Cymbals and bells ring with that natural tone you hear at a concert, horns blow your hair back, the right vocal tone sends chills down your spine, you can hear bass strings vibrate against the fingerboard and feel organ pedals compress your guts. Get the arm a bit too high, strings and horns go shrill. Get it a bit too low and you lose definition.
Further: "Is it achieving the perfect VTA? Or is it achieving the perfect overhang?"
I would suggest that it is probably VTA. I say this because there are several alignment schemes that can be used, and more elaborate protractors like the Feickert allow users to select which one they might prefer. There is no absolute right answer. Get VTA wrong though, and you can immediately hear it. Considering those two points and knowing how sensitive my VTA OTF arms are to changes in height leads me to feel that overhang and VTF are perhaps less critical than VTA and azimuth. This is probably due to the minuscule contact area between the stylus edge and the groove. It has to be in close proximity to angle at which the record was cut to get all the information out. A bit of skew to one side or the other might have a slight effect on image, but can't say about how significant that might actually be.
Other experiences seem to support this. A lifetime of playing warped vinyl until I found the Vinyl Flat is one. If I got the VTA right on a track that was essentially flat, everything went awry as soon as I hit the warped area. Very irritating. My second table is a 70s vintage Pioneer with an S arm and fixed VTA. It's reserved for less than pristine vinyl and recordings that can't benefit from better transcription. I put as precise an alignment on it as I could manage without investing more than a few bucks and if I drop a thicker record that was made in the early 60s, one of the dynaflex flimsies or one of the newer 180 gram pressings on it, it sounds awful. Harsh and brash when too thin and muddy and indistinct when too thick. Put on some Who or Floyd pressed in the era it was made and it's up to the task.
I've also fiddled around with VTF on the Pioneer to see what there was to hear. I have a very repeatable digital scale that resolves to hundredths of a gram and has a tolerance of + or - 0.02 g, so it's a simple matter for me. The factory recommended 1.8 grams for the Ortofon 2M Red is indistinguishable from 1.7 or 1.9 to my ear. That's about 5.5% of range, and a greater percentage of tolerance than that for either VTA or overhang adjustment. Accordingly, worrying over minute changes in overhang or VTF that could potentially occur from adjusting VTA OTF seems fruitless.
Some über-wealthy vinyl geek may set up a laser interferometer to finally resolve all the mathematical particulars, but I've found the solution that works well enough for me. It's easy, fast, reliable and makes my world a happier place because the music sounds so much better. And that's really what this hobby is all about.
