100Mbps and Gigabit switch on the same LAN
The GB devices will communicate through the switch at GB speed but any traffic transiting the router will be limited to 10/100.
Hubs are a thing of the past. All recent devices are switches. Each line runs at full speed. Occasionally there is an autonegotiation problem and a line is set to the wrong speed, but this is not directly related to having other slower devices on the same switch.