ToME: the Tales of Maj'Eyal

When the addons say the game version required, does that mean the exact version or minimum version? Because if it's exact it seems a lot the mods will be incompatible with each other.

Minimum. In general, ay version above that will work (used to be version specific), though if something in the main game changes newer versions may or may not continue to be compatible. But for the most part, anything above X version will work.

By design it is exact, but you often can manually load lower version addons at your own risk. Though sometimes some conflicts, or errors due to lacking functions may encroach. So even though you usually can load lower versions but it is not guaranteed to be compatible or required, especially if release versions differ.
So caution and carefull experimenting with old addons required if you don't want to guess why here skill doesn't work, or work differently, as well as why this lua error here.After all the game on it's own quite stable, if you don't count chronomancers, but those have no bugs, just anomalies.