Build a custom chatbot with Langchain

I want to build several custom chatbots with different system prompts. It would also be great if it could store the convo history, so that if a user leaves and come back to it a few days later, it will still see his convo, exactly like in chatgpt

I thought of creating assistants, and calling with different thread_ids.
Do you recommend to do it this way ? Can i do that using langchain ?
Thx !