Luthier, anyone; which ram is which?

[Flyby]

With the release of Oleg's new sim just around the corner, I look forward to streaking low over London (either in pursuit or being pursued). I'm thinking of finally building a new gaming rig, and have a question about those scenes being rendered fluidly: which ram (spec) will that be most impacted by? System ram, or video ram? Or am I way off base as to what will help render smooth frame rates low over London?
thanks for the advice/technical sharing,
Flyby out