One man's top dollar is another man's junk. How much do you want to pay?

Video memory does hold textures, but only for when you're displaying them in real time, as in a game, or in Poser preview. You didn't say anything about Poser preview performance, just rendering performance.

The video card does not participate in rendering in Poser. It does not offload your memory, nor your CPU.

Item 3, the cards for gamers, is all about real-time rendering. They won't speed up Poser renders, only preview.

Item 4: You can be sure that no card would speed up rendering. That's why the most common answer is no, because that's correct. A faster card with more memory will not off load the processor at all. The processor is not needing help with drawing on the screen while rendering. It isn't doing any meaningful drawing at all, except the little bits that show up as each block is finished.

---

Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)