text is mostly beaten to death, so you can expect good defaults to work for vllm. VLMs specifically are quite sensitive to quantization, especially if you want it to do fine-grained localization (time or spatial), and the vllm default params can be way off for your use-case.

For example, most vision models don't need 256K context length for modes like Qwen3.8-27B when all you care about is single-image captioning, so you can technically save on KV cache. Video reasoning does require that context length, so it's a different set of deployment parameters that need to be enabled.

All of this to say that the providers that offer these models, are simply using vLLM / SGLang, and mostly cater to the text inference use-case (coding, etc). Vision always seems to be a bit of an afterthought.