The NVIDIA press release [0] says "Each Project DIGITS features 128GB of unified, coherent memory and up to 4TB of NVMe storage", which makes it sound like the RAM is fixed size.
Maybe there will be storage options of 1,2,and 4TB and optional 25/100/200/400 GBit interfaces. Or maybe everything except the CPU/GPU is constant, but having a 50%, 75%, or 100% of the CPU/GPU cores so they can bin their chips.
Running a 96GB ram model isn't cheap (often with unified memory 25% is reserved for CPUs), so maybe it will win there.