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

When I was building slate plinths for various of my turntables, I adopted the practice of not creating any tonearm mounting boards or accommodating for them.  I therefore had to limit myself to surface mount tonearms, like Chakster says. These included the Triplanar, Reed, Dynavector DV505 and maybe a few more that I don't own.  I bolt the tonearm directly to the plinth.  Nothing moves.  I am not saying this is the best way to go; it certainly is not the most convenient nor the most flexible, but I think it adheres best to the principle of coupling the tonearm pivot to the platter and bearing.  For highest flexibility to use any arm any time, an outboard platform would seem best, if you're being pragmatic above all else.  A very heavy outboard arm pod that sits on the same support structure as the plinth itself is probably an acceptable compromise as far as coupling.

I think that it was Einstein that said  “Does the Station stop at this Train”

Now I know that I’m stretching the point a little but as Atmasphere said, to paraphrase..Relative movement between the arm mount and the platter is a bad thing.  We can have them both move in sync, within reason. 
If you agree with this principle, the arm mounting design options are narrowed considerably.

Thanks for all the information.
 I am considering a direct mount tonearm.
is there a sonic difference between Reed 3p and 2a

Yes.

The mounting of the platter bearing in the plinth will be thus coupled as rigidly as possible to the mounting of the tonearm. If it is not, any vibration at all can be interpreted by the pickup (arm and cartridge) as a coloration.

That's the advice you get from 'amateurs'....🤪
HERE is the 'reality' from Mark Doehmann, responsible for the designs of the Continuum Caliburn and Criterion turntables as well as his own Doehmann Helix 1 and Helix 2 turntables.....all of which are carefully designed with the tonearm mounting bases ISOLATED from the bearing and plinth 👍