These names sppear to be based on the real-world Bantu languages. These languages are very prominent across East and Central Africa, the most famous of them being Swahili.
Exempt-Medic has very helpfully provided some excerpts from the 1e campaign setting book:
The countless dialects of Garund’s Mwangi tribesfolk share enough remnants of a mysterious root language that members of different tribes from vastly divergent regions of the Expanse can generally understand one another even though they appear to be speaking completely different languages.
Countless related languages certainly sounds like Bantu—there are a lot of them! Though the real-world Bantu languages are less mutually intelligible than the Mwangi languages described here.
Zenj names are usually short and clipped, with hard consonants and many glottal stops and clicks that cannot be easily transcribed in written languages (! equals a velaric clicking noise in the back of the throat or velum and ‘ is used to denote a glottal stop). The Bekyar have their own, seemingly unrelated, forms that use many sibilants followed by hard consonants.
Aha, so we have click consonants! I'll get to those in a bit.
jukamis - joo KAH mihs
Mwangi - MWAN gi
Sargava - sahr GAH vah
And these are definitely sounding like Swahili so far, with the way the stress falls. Swahili is both the most famous Bantu language and one of the very few that doesn't have tones, so it makes a good reference point; for the rest of this answer, I'm going to be pronouncing words as if they were Swahili as much as possible.
Now, for your questions:
- Are x's pronounced as
sh? E.g., is Xanmba shahn-mm-ba? Is it different for the "Xh" in Xhokan?
The letter "x" isn't common in the Bantu languages. To my knowledge it's used only in the southern languages that have picked up click consonants from Khoisan, such as Zulu and Xhosa.
In these languages, "x" is a lateral click and "xh" is an aspirated lateral click. These are sounds that are very hard to describe in text; you make them with the sides of your tongue against your teeth. Wikipedia has some audio files, and you can also find Xhosa lessons on YouTube. The best description I can come up with is it's the sound you make to get a horse's attention.
Fortunately, that's the most difficult part of this answer from an English-speaking perspective. The rest of it is more straightforward.
- Is the
tz in Tzeniwe the same sound as the ts in the Japanese つ[tsu]?
I'm not aware of any Bantu languages that uses "tz", but that would be my assumption. Just a T sound followed by an S sound.
- Is the
e at the end of Tzeniwe its own syllable (tzen-i-way) or silent (tzen-eew)?
Its own syllable. Bantu languages don't tend to have silent letters: I would pronounce this tseh-NEE-weh. (The final vowel is somewhere in between "eh" and "ay", like the Spanish e. Spanish is a good reference for all the vowels here, honestly.)
- Are consecutive vowels pronounced together or individually? E.g., is Magaambya four syllables (
mah-gahm-by-ah) or five (mah-gah-am-by-ah)? Is Ekujae three (eh-koo-jay) or four (eh-koo-jah-ay)? Is Yaoua two (yow-ah) or four (ya-oh-oo-ah)?
Separately. Each vowel is the core of its own syllable, and should be pronounced on its own. In Swahili, the stress falls on the second syllable from the end, so Magaambya would be mah-gah-AH-mbyah. (That last bit is all one syllable; y is always a consonant in Swahili, never a vowel.) Similarly, eh-koo-JAH-eh, yah-oh-OO-ah. I'm not used to seeing four vowels in a row in any Bantu language, but that's how the writing system works.
(On the other hand, Patta has found a comment by a Paizo developer saying they pronounce "Ekujae" as e-coo-jay. So the intent may be to pronounce groups of vowels together, unlike in Swahili; in this case, it could be eh-KOO-jay and yah-OO-wah.)
- How are m's handled when there isn't a vowel with them, as in Xanmba or Mzunu? Are they separate sounds/syllables, or do they run together with the letter before or after?
The combination mb is its own sound, like a B sound with a little bit of nasalization before it. But if you have trouble pronouncing this, you can break the M out into its own syllable. If the mb comes in the last syllable of the word, you always break the M out separately to make it two syllables long: mbwa "dog" is pronounced "MM-bwah".
The combinations mv, nd, nj, nz, ny, and ng are their own sounds too, just like mb. But again, if that's hard to pronounce, it's fine to separate it out. The difference between MWAH-ngee and MWAN-gee is not significant. So, [click]AHN-mbah, [click]AHNM-bah, or [click]AHN-mm-bah.
When m or n comes before other consonants, it gets its own syllable: mm-ZOO-noo.
