What is the difference between MYSQL & SQLite?
SQLite is a embedded database engine, which is usually used by one application accessing it at a time. It's not as scalable as MySQL but its a lot lighter.
SQLite support is being dropped in SMF2.1 so I would suggest using either MySQL or PostgreSQL, both of which are supported.
The following sums up the differences between the three quite well;
https://www.digitalocean.com/community/tutorials/sqlite-vs-mysql-vs-postgresql-a-comparison-of-relational-database-management-systems
use mySQL - plain and simple...