Ok, I think I was missing that single packages for smartphones are 64-bit, and those are usually going to have the largest capacity on the market before anything else.48GB and 96GB should be possible, but the highest density 32-bit LPDDR5X packages are 128Gb (Samsung and Micron at least, SK Hynix has horrible public part data but I'd be surprised if they were higher) which makes the maximum capacity 128GB.
I think it will be rare that anyone would want to pair a dGPU with Strix Halo. You might want to do it when retiring the board from AI purposes years after getting it, or to enable some feature not provided by the 8060S iGPU (like DLSS or pre-50 series PhysX acceleration). Otherwise, you have a roughly 7600 XT GPU with "unlimited" VRAM to play around with.The main downside is if you want a dGPU. There, it seems the most they could do is PCIe 4.0 x8. That's still enough for mid-range GPUs.