Customizing Your Origin and Reincarnate

Question

The druid spell Reincarnate says "The reincarnated creature recalls its former life and experiences. It retains the capabilities it had in its original form, except it exchanges its original race for the new one and changes its racial traits accordingly."

Tasha's Cauldron of Everything includes optional rules for "Customizing your Origin" (pp. 7, 8), which allows you much more flexibility in assigning the ability score modifiers, languages, proficiencies, and personality obtained as "racial traits".

In the case that Tasha's optional rules are in force, and with DM approval, what happens to a character that is the subject of the reincarnation spell?

Are the original choices made at character creation 'imported' to the new form?

Are the new racial traits able to be modified freely, as the old ones were at character origin?

Or does the new form possess the 'standard' racial traits of its race, since Tasha's specifically applies to character creation?

There are several related question on how reincarnation affects racial traits and feats, but none specifically address the customization option in Tasha's:

If a Variant Human is Reincarnated, would they lose the feat and skill proficiency they started with?

Do you lose racial feats when Reincarnated out of your race?

How does reincarnation affect feats and ability score increases?

How are bonus feats affected by reincarnate?

Answer 1

Ask your DM.

Using options from Tasha’s in the first place is going to be up to the DM, so the outcome of a spell that wasn’t written to work with Tasha’s racial options is going to be up to the DM.

RAW, reincarnate obviously references the “non-customized origin” version of those races, since it is a Player’s Handbook spell.

Answer 2

They change accordingly.

Expanding on Thomas Markovs answer:

Even without the optional rules introduced with Tasha's cauldron of everything, racial traits that allowed you to make a choice were lost (eg. the free feat for the Variant Human). This means you would lose all racial traits as you would without the optional rules. Depending on what you rolled on your d100 for reincarnate you would be able to choose the draconic ancestry for your new dragonborn or the new language for your new human, so it wouldn't be unreasonable to say that you could choose completely new things. Even without the new rules a character might suddenly know how to fight with a longsword and there is nothing in the rules of the reincarnate spell that states that you reincarnate as a stereotypical depiction of your new race which means that with the new rules you technically could transform into a drow with proficiency in acrobatics instead of perception. Just because you couldn't do so without tashas doesn't mean it is prevented by the rules. Which it isn't.

But in the end I have to agree with Thomas Markov.

Its up to the DM whether or not you are allowed to.