The OpenAI Assistant nodes that you were referring to are exclusively built for the OpenAI Agent/Assistent (What you have in the OpenAI API playground under Assistant).
You could also use our AI Agent node and hook up the OpenAI Chat Model, which would generally work in the same way. We built the AI Agent node as a replacement for the OpenAI Assistent node, but with the AI Agent node you could connect other models too (e.g. Ollama, Mistral etc.).
Below an overview of the three “categories” described above.
I hope this clarifies it a bit But let us know if there’s still anything unclear!