Tonearm mount to the plinth vs arm board vs rotating arm board vs isolated tower

The best for me is armboard on the rails to change Pivot to Spindle distance quickly for various tonearms when needed. This design invented by Micro Seiki for Luxman PD-444, PD-555, PD-441 series back in the 70’s.

If you will look here such metal armboards mounted on the rails and can be moved left or right, they are fixed with lock. Clever design! The "plinth" of those turntables are metal (damped inside).

In modern design i see something similar on Dr.Feickert's turntables.  

Yes there is a difference that said is your plinth with these options 
going to be your final build/purchase or a test bed.

I built a plinth that accepts various arm lengths with multiple 
armboards. I decided the pivoting option was not for me and went with boards mounted directly to the plinth. Also various materials 
of construction for comparison.

One difference is the boards do not touch the exterior surface
and are attached to next layer below via threaded fasteners.

All sorts of opinions out there and some are easier to execute 
than others.

https://forum.audiogon.com/users/totem395

For practical reason this type of Steve Dobbins plinth for Garrard 301 is universal for different tonearms if you're going to use many. 
Same construction in Stereophile article 

Aesthetically Artisan Fidelity 301 is the best (imo), but you need many armboard to swap tonearms. 

Dear @kanchi647 : 1+  with millercarbon advise.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.