I purchased the Digirig Mobile - RS-232 a couple of months ago for my FT-950. I also want to look at using it for my VX-6. The product description for the VX-6 cable says any model of the Digirig mobile would work, but the description for the Digirig Mobile seems to indicate I need the Logic Level version.
Digirig’s serial port configuration is of no consequence when interfacing the radios that don’t use this feature like HTs for example. You can use your Digirig Mobile in RS-232 configuration with your Yaesu VX-6R.