Are cutting lathes VTA constant across the board?

No.

Yes.

what Dover said….. even the lead out groove…..

I thread is usually enough.

David Shreve, Guru on this topic, published these adjustments a long time ago using Rabco arm of 7 5/8"
 +/- height
Nautilus            +0.0058"
RCA, Vanguard        +0.0047"
Columbia pop        +0.0043" 
M&K RealTime        +0.0019"
A&M, Arista, Flying Fish, Performance Recordings, Warner Bros. 0.0000 
Telarc              -0.0012" 
English Decca, DGG  -0.0028"
Nonesuch            -0.0036"
Musical Heritage Society (some) -0.0085"
Columbia classical -0.0118"

I'm sure it's important but once the cart is set, I just play the disc. 

I adjust VTA for

1 - normal records - using favourites

2- 180g records - using favourites

Then jut run the 2 settings.

All my arms have VTA on the fly - but I run the 2 settings - otherwise you would go insane.

Unfortunately, historically cutting angles are all over the place - USA/Europe - then individual pressing companies vary a lot.

Furthermore, as regards RIAA standards - thats another story. Varies from recording studio to studio - some engineers compensating for the turnover frequency issues, some not, all dependent on what cutting amplifiers and heads were used.

Or do different mastering engineers have preferences on the angle of the cutting head? If they have differences, isn’t fine tuning VTA on you turn table just going to run you in circles with each different lol you play?

The cutter head has a stylus which is used to cut the groove. It lasts about 10 hours so has to be changed. The new stylus requires the head be removed from the lathe for installation. They are not all exactly identical. When installed, the engineer has to set up the operation as best he can- the ’tracking’ force, how perpendicular the cut is and so forth. After the initial work is done, then the process of doing test cuts to create the most silent groove is done to insure the cutting angle is correct. This is a combination of stylus temperature (its heated by a tiny coil around the base of the stylus) and the height of the rear of the cutter head (similar to the VTA setting in playback).

As a result the actual cutting angle of ’92 degrees’ is an approximation and has nothing to do with the label, the vintage of the LP or any such like. What is important to the engineer is that the groove is silent; the cutting angle is secondary.