Conversational AI + question answering model

I would like to train a model that does both conversations and questions answering based on articles we feed to it, and ending up with an informed chatbot. Is GPT-j-6B the way to go ?
There may be trade-offs to make in terms of performance, model size, training time, hardware resources. Could you suggest the best open source models that fits my goals? with different sizes and If I can train them with hugging face APIs. Thank you.