I have noticed that these types of enchantment power applications are not working correctly. It is also impossible to use vanilla armor, weapons from mods that support Spell Power (like Simply swords).

This formula is correct.

In the enchantment configuration Operation property value is "ADD".

But at the same time, multiplication always occurs.

No armor/enchants

Full Sunfire V set (0 * value * level = 0)

I think it's because the mod's initialization uses multiplication for all schools of magic with the POWER trait (arcane, fire, frost, etc.). Operation parameter in enchantment configuration does nothing, changing it doesn't affect anything.

The enchantment system on this legacy version is underdeveloped, due to the limitations of the old game version.
There is no development capacity to backport the new enchantment system of the game introduced on 1.21.

How does the enchantment system differ for version 1.21?

Completely rewritten, data driven, fully supporting attribute modifiers.

The tooltip shown on these screenshots, gives an estimated damage output. This estimation, might be buggy due to not including enchantments. But in reality damage done is increased.

thanks, i will try to move my build to 1.21