Hello,
For your design, if the majority of the FETs are 1.8V and you have some 3V FETs that require 3V for the gate while using 1.8V for Vds, you should consider the specific requirements of your design and the characteristics of the pads.
Given that your core voltage is based on 1.8V, using PVDD3AC would be appropriate. The PVDD3AC pad is typically used when you need to interface with core voltages of 1.8V while still providing 3V for specific IO requirements.