Poa is more like "cool" - more informal and slangy than nzuri. It's a different register and it's the standard response to mambo. I'm translating below to give a sense of the formality rather than literal meaning.

Mambo (vipi)? - What's up? Poa. - I'm cool./Not much.

Habari (gani / za asubuhi / ...)? - How are you? Nzuri. - I'm fine./I'm well.

And then there's shikamoo which is extremely respectful to elders and apparently comes from an Arabic word and literally means "I touch your feet", and the reply to that is marahaba.

m/n/zuri means nice, good. Poa means cool or cool down.

"Mzuri" means good but this word will be used when referring to humans or animals. If you wanted to ask about the film and I were to reply "good", I would use "nzuri".

Mambo is the question poa is the reply.

or as a descriptor of something. It's an adjective. Or an instruction. Or a reply for sorry (pole) I'm already calm (nimeshapoa).

No that would be 'kazi poa'.

You mean poa and safi ? Nothing much just like tayyeb and jayyed.

You could use poa but great means kubwa.

Yep, even the word for table is similar.

Yeah! I was going to comment that :)

Wasn't that area Portuguese colonies at one point? Id assume theyd have a lot of Portuguese loan words