Qwen 3.8 27B defaults to "xhigh" (its maximum level) for thinking, which makes it diabolically slow. Setting it to "medium" or "low" speeds it up a lot.
I had to hack the template of Qwen 3.8-27B to get it to go into low reasoning mode. Not sure if that is fixed.
Have you tried Nemotron 74B-9B? (Slow on Mac with llama.cpp due to a missing tensor type)