The Prime core (Kyro 485) on the Snapdragon 855 Plus is clocked at 2.96GHz compared to 2.84GHz on the regular variant. The other CPU clusters and core including the 4x Kyro 385 cores are clocked at the same speed as the regular variant. For more graphics horsepower, the Adreno 640 GPU inside the Snapdragon 855 Plus is clocked at 672MHz which offers a 15% increase in graphical performance compared to the GPU on the non-Plus variant.
Apart from the higher clocked CPU and GPU, the Snapdragon 855 Plus is the exact same chip as the regular Snapdragon 855. Qualcomm is likely able to offer the Plus variant due to the process node improvements in TSMC’s 7nm fab. It is essentially taking out the higher binned SKUs of the Snapdragon 855 and selling them to vendors with higher clock speeds.
Qualcomm says many vendors will announce Snapdragon 855 Plus-powered devices over the new few months and weeks. All major flagship smartphones due for launch later this year should use this chipset including the OnePlus 7T, Galaxy Note 10, Asus ROG Phone 2, and more.