The Immortal of the Great Tang

The protagonists are a brother and sister: one owns an antique shop, while the other is a researcher at an archaeological institute. They were only joking around with people online about which ancient Chinese dynasty they would choose to transmigrate to, when they unexpectedly transmigrate and obtain two Systems that let them travel back and forth between the past and the present. Everything changes. One pretends to be an immortal, the other poses as a deity, and in the end they choose the early Tang Dynasty. The course of the empire begins to change.