As Atronachs are Daedra, they originate from planes of Oblivion. Oftentimes a certain type of Atronach can most commonly be found in a pocket realm matching their nature. For example, Flame Atronachs come from Infernace, Storm Atronachs come from Levinace, and Cold-Flame Atronachs come from Takubar.

What counts as a Daedra?

Daedra (singular: Daedroth) is the term for the entities who inhabit the realms of Oblivion in The Elder Scrolls. They are viewed variously as gods or demons by the inhabitants of Tamriel, although scholarly consensus discourages the use of the latter term.

Does conjured Daedra count as Atronachs?

Although casters must have a high Conjuration skill to summon a dremora lord, Perks are neither required to summon one nor do they raise its strength. The dremora lord is not affected by "Elemental Potency," as it is not an Atronach.