In terms of speed, groq.com is probably fastest and it runs open-source models only. They have specialized hardware and they claim to be the fastest in AI inference. Whatever.. they have a free tier so you can always try for yourself.
As for the big guns, Gemini from Google is also fast, at least compared to ChatGPT free. The quality is similar to open models but below ChatGPT on certain tasks. Sometimes better, sometimes worse, it depends on your use case.
If you only need speed, run a TinyLlama or other similar small model on vast.ai . But quality is submediocre.