OmniTrack will upload all the information about the customers who visit your store to Facebook as much as possible. As can be seen from the "Coverage" part in the example picture, OmniTrack uploads 12 customer information to Facebook.
And in the "Recommendation" part on the right,Facebook recommends that you can upload 4 more items of customer information, including the "External ID" . OmniTrack will pass on the "External ID" to Facebook, but only if your store has a login feature. Once the user has logged into the account, OmniTrack will automatically pass the "External ID" to Facebook.
OmniTrack cannot upload to Facebook the three customer information of Facebook Login ID, Date of Birth and Gender, because Shopify cannot provide these customer information.