A great example of this technique comes from P!nk. At 2:03 in “Walk Me Home,” she sings the chorus an octave below, accompanied by nothing but an acoustic guitar, which makes the final chorus that returns later all the more impressive and memorable.
“FEFE”: Welp, almost none of the section lengths here are standard. The bridge is really like some kind of early outro that incorporates the refrain, and then the outro-outro also mixes in the refrain, just in a different way. Who even knows anymore?