If anyone with a C1 Venture X happens to be flying out of T4, it would be great to see if VS lounge access is allowed using the VX card. It seems Capital One does have a special arrangement with Plaza Premium and VS for access that is separate from the usual Plaza premium contract that AmEx and others have. Based on this article -
VFTW - Capital One cardholders VS lounge access
This seems plausible given that the other C1 lounge(s) will also be operated by Plaza Premium.