With the option 'Add new participants', existing email addresses and data enrichment are skipped, and therefore not added again. Only new email addresses with data enrichment are added.
With the option 'Add new participants and update existing participants' you update the data enrichment of the existing respondents and add new email addresses and data enrichment.
Do you want to add participants or data enrichment? Read more information about adding participants or data enrichment here.
Do you want to remove certain data enrichment? Read more about removing data enrichment here.
Do you want to remove certain columns for the GDPR? Read more information about the retention period here.