I have used a Google product called NotebookLM. The advantage is that it will only look at the sources you provide. You can add youtube videos PDFs links. I think that this increases the quality of the answers.
I use a Google doc and paste in information that I find that is relevant. On a free account you can only add 30 sources, but the sources can be a large as you want. By adding content to only one Google Doc it reduces the # of sources..