Subject/pronoun-Verb Agreement with ser

[rparmst]

This is something I should have learned like my first month of Spanish, and I am embarrassed that I do not know it:

Obviously conjungation of a verb depends on the subject (Yo voy, Tú vas, etc).
With the verb ser, if you use a pronoun + ser to say that the person equals something else (predicate nominitive), does the conjugation always match the pronoun, which could be be the subject or the predicate nominitive, or does it always match the subject of the sentence, whether or not it is the pronoun?

Examples:

A. Tú eres mi felicidad. (Tú is the subject, so we choose eres.)
But, if subject and predicate nominitive are reversed:
1) Mi felicidad es tú.
--or--
2) Mi felicidad eres tú.

B. Yo soy el camarero. (Yo is the subject, so we choose soy.)
But in reverse:
1) El camarero es yo.
--or--
2) El camarero soy yo.

I would think that in both cases option 1 would be correct because the subjects are felicidad and camarero, but I recall a billboard in Santo Domingo that said, "Lo que importa eres tú," which leads me to think that ser is always conjungated to match the pronoun, regardless if it is the subject or predicate nominitive.

Thanks!