Is extremely accurate "VTA" adjustment necessary?

With any pivoting arm, the effect of azimuth variation and skating force variation over the playing area of an LP will swamp out any effect of VTA variation between LPs. If you are serious about vinyl, get a linear tracking arm.

Having long since gone to a linear tracking arm, it is some time since I had to make all those critical adjustments. However, for most pickup adjustments, the technique of inverting one channel, AT THE PICKUP BY REVERSING WIRES OF ONE CHANNEL, is probably better than any measurement method. This approach adjusts the axes of pickup sensitivity (what you hear) rather than some mechanical axis that, even if perfectly measured, may, or may not, correspond to the axes of sensitivity.

Tbg...True...if you run one phono pickup channel with inverted polarity you need to invert other inputs of that channel. I did it with electronics modification, but you could also use a simple "knife type" switch in the speaker circuit. There are a number of advantages to running one channel inverted, which I exploited, but in this thread I was thinking only of phono pickup setup procedures.

I cannot begin to explain all the ways that a linear tracking arm eliminates the plethora of adjustments needed for a pivoting arm. The real problem with a pivoting arm is that many of these adjustments can only be correct for one or two points in the LP recorded area.

Your comment about the overhang, "if off, is off all the time", hits the nail on the head about linear tracking. Whatever the error, it's not changing, and can therefore be adjusted effectively.

My arm is servo controlled, and does not care about level. Some linear tracking arms were demonstrated playing the record upside down! A stunt, of course, like Fritz Kreisler playing his virtuoso violin encores with the instrument held upside down.