Is it possible to test app performance in different network conditions, such as 2G, 3G and 4G?

You can now simulate different network conditions to test the performance of your apps. When you run your tests with the default network settings, each device will have an unhindered WiFi connection with Internet connectivity. With Network Simulation, you can change the WiFi connection to simulate the speeds of network profiles like 2G or 3G that controls bandwidth, latency and packet loss. For more details refer to the Network Simulation documentation.