How would the regions best be described, assuming the entire world map.
The Middle Lands
Shadowreign? (past, Atomos)
The Eastern Lands (Aht urhgan)
The Far East (Reisenjima, east from above on world map on same continent
The Western Lands (Adoulin)
Otherworld areas (Escha, Dynamis, Promvion, Abyssea
With what, real world analogues or just how would we describe them?
There's no need to distinguish between Shadowreign and Middle Lands, since those are both just under Middle Lands.
Middle Lands I'd describe as incredibly mountainous, riddled with caves, and mostly desert (Altepa, Terrigan, Valkurm, Gustaberg, All of Mindartia except Zitah, and arguably Xarcabard since there's never rainfall).
The Near East (Ephramad, Aht Urhgan) are basically analogous to Turkey and The Middle East IRL. Apples are native to there in the real world(Kazakhstan in particular). Very much more like Turkey. They likely skipped out on deserts because we already got so much of that in the Middle Lands. Likely that there's deserts further east though, wherever it is they're clashing with the Far East. Heavily forested with deciduous trees only.
Far East is clearly supposed to be Japan/SE Asia inspired/implied.
Dynamis is a dark dreamland reflection of the Middle Lands created by Diabolos to be a repose laden paradise but infected by Raogrimm's Shadowlord persona.
Escha as far as I recall is the future state of the Middle Lands when swallowed by Cloud of Darkness's miasma or whatever the hell it is, but they've been wrenched back in time. Just more or less a radically altered version of the Middle Lands sutured inside of the Middle Lands in the same way as Dynamis by a different entity. It's almost like instead of a reflection, the future literally turned around and fell on top of the past, map wise.
Promyvion is a pocket dimension created by the Emptiness Selh'teus brought with him to infect the Mothercrystals so that he could get their light to Al'taieu. The areas themselves are more or less mothercrystal prolonged pocket dimensions which exist alongside each infected mothercrystal. I mean, for sure, they are the result of Emptiness being brought in direct contact with each mothercrystal.
Abyssea is literally just an exact reflection of Vana'diel as a whole, damaged and close to extinction.