ust_client_event - Events stored linked to a specific pageview, session and user.
ust_ab - Stores AB tests
ust_users (internal) - Stores list of UXWizz dashboard users
ust_access (internal) - Stores which domain data can be accessed by which users
For improved performance, there are multiple indexes already created. Those indexes are specifically created for the queries ran for the UXWizz dashboard, but they should also lead to very fast query performance in most cases.
You can find many example queries in the PHP source code of UXWizz.
Usually each PHP file only runs a single query.