Adapting community auth to an existing database

This project is my first professional experience and I'm having a lot of trouble deciding among frameworks, plugins and etc.

I found CodeIgniter simpler than Laravel and attractive, but my project requires different access levels, so I went looking for a plugin. After a while, I found "Community Auth" which seems active and secure enough. I went through the installation instructions until a step where I had to run an SQL script.

Problem is, I'm working on a relatively simple project that shares a database with a mobile app that's being developed by another team and I don't want to mess with that too much. I understand the need for the creation of tables like "auth_sessions" and such, but the script includes a complete "users" table and I feel like altering our current one on our project could have unwanted effects.

I know I can use /config/db_tables.php to rename the users table, but can I map the fields to existing ones? Should I look for another plugin? Should I switch to Laravel?

I asked it on StackExchange, but it's probably better to post it here.