I will do my best to answer the questions above.
1. What is meant by "show" them the data source? The ability to view the data can be controlled within the user permissions of the Tableau Server.
2. The data source will need to have the password embeded in the workbook when published to refresh on a schedule: Schedule Refreshes on Tableau Online - Tableau . The data can also be updated with the Tableau Online Bridge client: Use Tableau Bridge to Keep Tableau Online Data Fresh - Tableau
3. The speed of the publication could be affected by having the data source included embedded vs. not. But, if they are live data sources, I would not expect too much differential in publication. This can also depend on the number of sets, calculations, and other information that is stored in the .tds file.
Let me know if you have any other questions, though, I would encourage creating a new post so that it is at the top of the feed.
There is also another great resource for why questions might not have received a response in the Getting Started in the Forums space of the Community Forums that is a great read: So Your Question Didn't Get Answered... Getting Started in the Forums
Hope this helps!