Careful with ‘sync experts’ on YouTube and SM. There are a lot of ill-informed ‘gurus’ who think sync agents are the way to go, insisting you should keep all the rights to your music, and never give them away.
That might make sense for an artist or band that hopes to one day break out and wants to control all the rights as long as they can.
But for a composer just looking to add a healthy extra set of income streams from production music getting used on TV and advertising, it’s most likely MUCH MUCH better for you to work with great (effective, well connected) libraries that will do all the hard work long term of getting your music used. The income for you is passive as soon as you finish and deliver the music.