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

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.

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.

Well, I know Steve Dobbins. I have met him face to face and have had extended conversations with him about optimization of the venerable Garrard 301. Steve will tell you that the swiveling arm board is a compromise and is not optimum. It is a useful convenience feature. A very useful and very convenient feature but still a compromise. For optimum performance, he advocates mounting the tonearm directly to the plinth. No replaceable cut-outs, no extensions, fixed or rotating. Why should this be surprising when extensions resemble diving boards?
Everything needs to be kept in perspective. The Garrard 301 is not the ultimate in terms of being quiet or in terms of speed accuracy. Instead, it has it's own sound, a very good one. In light of that, one should not sweat bullets about having or eschewing a rotating arm board. They are clever and indispensable for those that want to use lots of different arms. The compromise in overall SQ is likely negligible. I would argue that it is only when using the very finest MC cartridges with the 301/401 that one should avoid any otherwise avoidable compromises.