Is there a best cartridge track force gauge?

Of all ... setup(s)...VTF is the easiest to optimize by ear

Actually, I agree -- as long as you don't get carried away over (or well under) the limits!
But a reliable digital gauge is useful to re-set a cartridge to an optimum setting found in the past.

Eldartford, my arm is spring loaded, the Ortofon, in this case the spring load would be off by more than you suggest. Generally, I agree that your ears are the better gauge, but there are interactions with VTA to consider also. The Ortofon cartridge at least in this arm likes a positive VTA (up in back). I have no idea why this is true.

While I agree that VTF and VTA are interrelated, as a pratical matter this need not be anything to consider on a day to day basis, if during initial set up you pick the mid range of the cartridge manufacturers recommendations for VTF and then set your initial VTA for the thickness of LP's you use the most. Once you have done this, then you can further fine tune the VTF and then the VTA by ear for that thickness of LP, and thereafter only the VTA for record thickness.

I can't imagine that anyone without dog's hearing could hear a difference in VTF caused by VTA changes for different record thicknesses. The obverse would not be ture at all.

Although its going to be considered a heresy on this forum, you can make minor VTA changes when you're lazy, by merely rotating the counter weight on your arm, assuming that it has settings marked so you can return it to its original settings after your done. This works especially well for those without the ability to do VTA on the fly. The key word here though is "minor".

One thing to be careful of with many digital scales, including mine, is magnetic attraction. If I dropped the stylus directly on the platform as Elizabeth does the pull between the magnets in the cartridge and the scale would make VTF far greater than normal. With my scale the attraction is so strong I'd be afraid for the cantilever.

This requires a doohickey of some kind to seperate the cartridge and scale, which secondarily affords the opportunity to weigh at record surface height.

Tbg...I did think of the situation where downforce is applied by a spring. My old Empire turntable worked that way, and I believe it is the best approach because the arm can be mass-balanced so that vibration effects are minimized. With a spring the VTF will be affected by arm angle, but the question is, how much. In the Empire the downforce spring was a multiturn clock spring, and I doubt that a couple of degrees would have much effect.

But I do wonder. Since you have an accurate gauge, perhaps you would favor us with some measurements.