What is the difference between a production company and an agency?
An advertising agency owns strategy and campaign: what to say, to whom, on which channels. A production company owns the making: how it gets shot, cut, and finished. A freelancer is one person with a camera or an edit suite , and can be excellent inside a scope one person can hold.
The practical test: if you already know what you want to say, you need a production company. If you do not, you need a strategic partner first, and some production companies do that too.