shoul psub2 be connected
In the case of TSMC process, PSUB2 is a dummy layer. It is used when you have multiple power (for example analog and digital) and you are not using deep nwell.
More concretly, let's say you have agnd and dgnd. When fabricating the chip the substrate is common so there is a connection.
You will have 2 diffrents ground pins, but they are connected so when doing the LVS it will generate an error.
Using a PSUB2 region for the digital (for example) the two region are not connected during the LVS thus making the use of 2 pins possible.
Hope it's not to confuse