Chatbot to assist platform users

Hello guys, I am going to implement a chatbot using RAG to assist users of a platform , for data i have emails (support responses to claims), FAQ, data from pages …, i am thinkin of usind a pretrained model and add rag db to make it domain specific , what do you suggest for the techs I’ll need ( embedding model, LLM, Vectordb) ,I’ll also need to add voice to text feature when text to text success.
Thank you sm for you help ,I am new to to this field and I appreciate your valuable help.