Yes, you can connect a switch to any Pod for your client connections; however, a switch should not be directly connected to a modem when it's used for client connections.
Each Plume Pod comes with an Ethernet port that supports both network or client connections, so you can hardwire your device or switch to any of the Pods to gain internet connection to your devices.
If a switch is connected directly to your internet modem, it may open your home to security attacks. You can tell if you have an internet modem if you ONLY have one Ethernet port on your modem. If you have multiple Ethernet ports on your ISP device, it means your device includes the router features and you are protected with a firewall.