I had to remove some of the older WiFi plugs as these clearly impacted my WiFi network. The more devices you add they compete for accessing the router. If they are cheap or stop getting software updates you’re inviting trouble. The other aspect is security. Many Smart home WiFi devices weren’t built with security in mind. If you do online banking from the same network, you’re inviting trouble. Every smart home expert will tell you to separate your smart home WiFi network, use another SSID, use VLAN. I chose to use z-wave and zigbee instead and slowly get rid of the WiFi smart home stuff.