Qwen3.8 27B Swift-1.5

User asks whether to switch from a Qwen3.8 27B Swift-1.5 Q6_K setup to a Qwen3.8 Flash-Next Swift-1.5 IQ3_XXS GSQ RCO quant for agentic work. Current setup runs at 262144 context with Q8/Q8 KV cache on 40GB VRAM across two Radeon VIIs plus an RTX 3080 Max-Q, with 64GB DDR4 RAM, using ROCm and Vulkan. It achieves around 450 t/s prefill at 16384 tokens and 15-30 t/s output with dflash2 speculation. User is unsure whether the lower-quant Flash-Next would be smarter at comparable speeds, and notes that a mixed Vulkan/ROCm backend rules out engines like Strata, likely requiring a custom llama.cpp fork.