SOTA NOVA, HR-X VPI, Technics 1200G recommendations?

@lewm, I promise I will not come back at you with airborne vibration 🤐
Exactly, I did not buy the Infinity arm because it was not stiff enough. I got a Syrinx PU 3 which was not a neutral balance arm but it was very stiff and no removable head shell. The removable head shell and it's socket are unnecessary mass at the end of the arm and an additional set of contacts. Maybe it is only a few grams, still IMHO unnecessary. Although the SME style locking mechanism is very stiff you are probably right, a fixed head shell is stiffer. The arm tube on my Schroder is dampened carbon fiber BTW. 
A stable balance tonearm increases VTF as it goes up. That is why it hunts for the balance point. The easiest way to tell is lift up the arm just an inch and gently let it go. A neutral balance arm will just stay there. A stable balance arm will start hunting up and down. It is not enough to have the counter balance weight at the level of the record. The center of masses at both ends of the arm have to be in line with the axis of the vertical bearing. I have played with a FR arm. I do not recall the model.
There is a lot you can tell about an arm by just looking at it. For instance an "S" tube arm is going to be heavier than the same arm with a straight tube. The straight arm will also be stiffer.  An arm with a removable head shell is going to have more mass than the same arm with a fixed head shell. The Kuzma is a great compromise BTW. Mass at either end of the tonearm is more significant than mass near the pivot. This is what effective mass is all about. Like a seesaw inertia is affected most b mass at the ends. Inertia is different than effective mass. 
Tonearm design requires a bunch of tradeoffs. Is there one right balance?
I doubt it. I prefer lighter arms and more compliant cartridges but there are limits as too how light you can go. Is the FR stiffer than say my Schroder. I seriously doubt it. IMHO the FR does not justify the added mass. For stiff cartridges I would rather add just as much mass as  needed to the Schroder. 

Technics for sure!
Still have my original 2 I bought a loooong time ago, still look and work as flawlessly as the,first week I brought them home.

and the sl1210 in black. All are like newish.
all start, stop, everything as new.
There is not a better RELIABLE TT made. In my opinion.

Removable headshell is amazing option!

I didn’t damage any cartridge on Reed 3P (without removable shell), but it’s a challenge to swap carts on such arms. If you want to use just one cartridge then it’s ok.
But I got many cartridges and many tonearms. I like and enjoy using tonearms with removable headshells and DIN connectors.

Some outstanding tonearms are: Ikeda IT-345, FR-64fx, 66fx, 64fx PRO, 64s, Lustre GST-801, Victor UA-7082, Technics EPA-100 mk2 and much cheaper Denon DA-401 for high compliance carts. All with removable headshells!

@chakster, for people who want to swap cartridges all the time removeable head shells are very convenient but, they are a compromise when it comes to performance. If I really needed a removable head shell  I would not get any of those arms. I would get a Kuzma 4 Point 9.
I have found that I only want to listen to one cartridge, the one I like best. With the exception of 78's the best cartridge is always best at all genres. I also do not mind setting up cartridges. I am not willing to compromise. I want the best performance possible considering the tradeoffs. Once I set up a cartridge it stays put for years, sometimes more than a decade. If comparing cartridges is your thing the best way to do this is with multiple arms. Unfortunately for me the only turntable I like that takes two arms is the Dohmann Helix which has not fully evolved yet and is currently out of my price range anyway. 

I can't disagree more, because I'm still searching for the "best" cartridge and I tried over 60 of them (new and old, mm/mi and mc). Using 4 different tonearms is better than using one. 

It was an illusion that I could use one great cartridge on one great tonearm, this is the reason why my Reed 3p "12 inch is not in use now. This is the reason why my most expensive modern LOMC are not in use now. 

In my perspective I only discovered something more interesting, more involving and it wasn't a compromise in sound at all. 

As I mentioned in my previous post, with tonearm (with removable headshells) like Ikeda IT-345, FR-64fx, 66fx, 64fx PRO, 64s, Lustre GST-801, Victor UA-7082, Technics EPA-100 mk2 and much cheaper Denon DA-401 ... no one can go wrong if they are in use with properly matched cartridges. I have all those arm and very happy about performance.