Qwen3.8 27B

User reports Qwen3.8 27B at 19 tok/s with speculative decoding on an RX 6900 XT 16GB. Setup is LM Studio with IQ4_XS weights on the Vulkan backend, single GPU, 32GB system RAM. Without speculation the same model and quant runs at 11 tok/s; a Qwen 27B Q3_K_M run gives 8.4 tok/s and a Qwen 4B gives 51 tok/s with thinking off and 38 tok/s with it on. User asks whether Linux/ROCm would beat Vulkan on Windows and whether these speeds are normal for the card.