Learn Spanish (Latin America): El nuevo confidente tiene mucha comprensión. - The new confidant has a lot of understanding.

Yes, the placement changes the meaning! When nuevo comes before the noun, it means "newly acquired" or "new to me" (this person just became the speaker's confidant). If it were placed after the noun (el confidente nuevo), it would emphasize that the person is literally brand new to the world or a complete newcomer to a group. Placing it before the noun highlights the change in relationship rather than the physical age or novelty of the person.

How do we know if a noun ending in -nte like confidente is masculine or feminine?

Nouns ending in -nte that refer to people are usually "two-way" nouns. The word itself doesn't change ending, but you use the article to show the person's gender. Here, el tells us this is a male confidant. If the confidant were a woman, it would be la confidente.

Why use tiene mucha comprensión instead of saying he is understanding (es muy comprensivo)?

Both are perfectly fine and natural! Spanish often uses the structure tener + [noun] (to have understanding) for personal qualities where English prefers to be + [adjective] (to be understanding). Using tener simply highlights that the person possesses a lot of this particular trait.

Why do we use mucha here instead of muy?