Sony has begun sending out emails about the Xperia X Performance Android 7.0 Nougat beta program. If you had signed up earlier, those who have been picked should have received an email in their inbox confirming participation.
Your Xperia X Performance will receive the OTA update to Nougat within 48 hours.
Sony's Xperia UI is one of the lightest skins on top of Android and keeps most of the stock functionality intact.
The X Performance was part of Sony's new line-up running on the Snapdragon 820 quad-core processor with 3GB RAM, 32GB storage, Android 6.0.1 Marshmallow.