Q: Vram windows and mac

The VRAM should be the same for both OSes, as it's determined by the GPU and the amount of RAM you have on the MacBook (in the case you have a Mac with an integrated GPU) or by the GPU (in the case you have a Mac with a dedicated GPU). For integrated graphic cards, see > http://support.apple.com/kb/HT3246

If your MacBook Pro has got a Intel HD Graphics 3000 or 4000, you need 8 GB to get 512 MB of VRAM for the graphic card

You have to buy 8 GB of RAM, as your MacBook has only two slots to put RAM, so you can't buy 4 GB of RAM to add to your existing amount of memory. You can buy more RAM at OWC or Crucial. Crucial is cheaper and sells supported memory

You are welcome