Macs with unified memory are economical in terms of $/GB of video memory, and they match an optimized/home built GPU setup in efficiency (W/token), but they are slow in terms of absolute performance.

With this model, since the number of active parameters is low, I would think that you would be fine running it on your 16GB card, as long as you have, say 32GB of regular system memory. Temper your expectations about speed with this setup, as your system memory and CPU are multiple times slower than the GPU, so when layers spill over you will slow down.

To avoid this, there's no need to buy a Mac -- a second 16GB GPU would do the trick just fine, and the combined dual GPU setup will likely be faster than a cheap mac like a Mac mini. Pay attention to your PCIe slots, but as long as you have at least an x4 slot for the second GPU, you'll be fine (LLM inference doesn't need x8 or x16).