What Do You Hear When You Adjust VTA?

I hear a shift between muddy slow plodding muffled sound (VTA too low)- to shrill, hurt the ears, ringing nastiness.
With my line contact stylus the correct setting is quite precise and the range of acceptable is narrow.

I agree, again.
One thing that has helped me a lot is to play many records within a boxed set. Then you can be pretty sure the pressings are more or less uniform in vinyl thickness and the cutting angle. One set I have has aprox 100 records in it of all different periods in classical music. You get harpsichord - very difficult if the VTA is too high - strings, organ music -plodding, poor muffled bass if VTA to low, voice (opera) which sounds a mess if VTA either way is incorrect.
Pretty quickly you can dial it in.