The site for X-Cart 5 developers is here:
There is no database chart for X-Cart 5 because the layout depends on installed modules.
There are many modules that alter the database, so any ready-made chart won't work for most of X-Cart users.
Originally Posted by classw
The second question: We are much better mySQL/Nodejs programmers than PHP programmers. What are the implications of just doing direct data inserts and updates into the data tables for adding/updating products, categories, and orders?
By sending direct queries you risk to break the database consistency. It is highly recommended to avoid this in X-Cart 5.
X-Cart 5 uses an ORM library (Doctrine 2). You can start reading about working with the database from there: