When I load yarn-mistral-64k in Ollama (uses llama.cpp) on my 32GB MAC it allocates 16.359 GB for the GPU. I don't remember how much the 128k context version needs, but it was more than the 21.845GB MacOS allows for the GPUs use on a 32GB machine. You aren't going to get very far on a 16GB machine.
Maybe if you don't send any layers to the GPU and force it to use CPU you could eek out a little more. On Apple Silicon CPU inference only seems to be a 50% hit over GPU speeds, if I remember right.