Summary
User compares three Qwen3.8 27B Q4_K_M quants on an RX 7900 XTX: the base unsloth quant, ThinkingCap and Swift, all run with thinking at xhigh.
The base quant decodes at ~48 t/s with ~530 t/s prefill, ThinkingCap at ~43 t/s with ~100 t/s prefill (TTFT 6-11s), and Swift at ~32 t/s with ~614 t/s prefill (TTFT ~1s).
Total tokens per 4-scenario run fall from ~66k for base to ~49k for ThinkingCap and ~45k for Swift, with quality in the ~84-87 band for all three; the user notes only 2 runs per quant and calls the ThinkingCap prefill oddly low.