So, if you adopt the principle that the mat ought to transmit energy into the platter (I don't disagree), you then have to worry about isolating the bearing and any other sources of noise, like even that which can be transmitted by the belt from the outboard motor pulley of a BD, from the platter and mat. Denon paid some attention to this issue in their higher end DD turntables, back in the 80s.
Damping between the motor bearing and the platter will allow the tonearm to pick up vibration that might exist in the plinth; the platter surface must be as rigidly coupled to the plinth as possible. To that end the bearing (which is usually low noise anyway) should not be isolated from the platter.
As for Mat's it is impossible to recommend a Mat for your set up, and listening environment that will work.
This statement is false. The job of the platter pad is to absorb vibration from the LP at all frequencies and to that effect isn't a tone control. If this is being done correctly it will benefit any system.
If you can hear the stylus tracing the groove in a complex passage with the volume all the way down from only a foot away from the cartridge, you know you have a problem with the mat. It should be dead silent even if you are only a few inches from the cartridge as it tracks.