Personalized Variant currently looks at session recency, session frequency, and tenure, and we are looking into adding other characteristics.
More context from the Fall Release and a link to the documentation:
Improve campaign conversions with Personalized Variant. A/B testing helps you determine which version of your message produces the best results, but it’s rare that one version of a message is truly the best version for every customer. After all, while most customers prefer Version A, a few might actually prefer Version B. Personalized Variant is a new optimization feature for campaign A/B tests that considers these individual differences and automatically sends each customer the campaign variant with which they’re most likely to engage.
