Maple platform under turntable, How thick?

Granite...
Would look like kind of cemetery.
To clarify one thing. The woofers of my speakers are way above the floor level, and I get least vibration near the floor so all of my equipment is right down there.

I am extremely happy with bearpaws at VermontAudio.com. This was a huge upgrade for my table.

One thing to keep in mind is whether you are trying to couple or decouple the platform from the floor. Cones usually couple, bearings decouple. One thing not mentioned is using partly inflated small tire tube to isolate the platform. I use to use slate, which is better IMHO than granite but harder to find. I used the deflated racquetball method under it, I haven't heard about this trick for a long time.

Do I want to couple or decouple? You mentioned cones and bearings. What about Walker things, you know, those three massive cones going into led-filled discs and two more discs on top?

As I said, there are many out there. If your floor vibrates then you want to isolate your table from it; if not coupling is fine. The only general rule I have discovered in audio is that there are no general rules and that what works best is determined by the particular circumstances of your system. That is why after 50 years in it I still haven't achieved Audio Guru-hood, I don't try to give absolute prescriptions from a distance; don't trust those who do.