4GB max, ok. I have 32GB and I am not afraid to use it! (well, most of it anyway.)
I should know this but I don't: that's system RAM not graphics card RAM right?
The Titan I have is around 6GB, my mobo has the 32GB, so in a way I have 38GB in system totality... sure would be nice to put it all to work. Heck this Titan card can reach up to 4.5 Teraflops of performance, which is supercomputer numbers back in the early 2000s. I am constantly dissapointed that it is rarely utilized due to software setting/restrictions, there should be a lucrative way for that not to happen and for software to better adjust more appropriately to the system it runs on.
I have no serious probs with 7DTD, just spit-balling and trying to learn more about system bottlenecks, etc. Talking in general here, it's not only games that fail to do this, have 3D modeling packages and other software that also under-utilizes the hardware at it's disposal.