The driver is a dll that is needed for authentication and establishing a communication channel with the database. They can be different and provide a basic API (the lowest-level database access). They work, as you put it, directly with the PostgreSQL protocols. It is for them that you write the server address, port, login, password, encoding,...

Component libraries (FireDAC, ZEOS, UniDAC, ...) provide convenient access to database functionality (Queries, Tables, Connection, Meta Information, Transactions, ...).

ORM is designed to hide low-level information about a database and work with information as objects. None of these components optimize your queries, no matter how much you want them to. There are separate tools for optimization, where you prepare the request.

If you are still in doubt, write a short application with your request and check how many bytes the server will return to you!