Qwen3.8 Flash Next thinking modes:
Low is not always worse than Medium, but I couldn’t identify clear cases where Low should be preferred over Medium. So I’d recommend Medium as the default for cheaper reasoning, and Xhigh when higher accuracy matters, especially for coding.
I could be wrong, but Low really looks like Medium with additional instructions (that you can find in the chat template) to reason less, rather than a separately post-trained reasoning mode.