Trouble understanding VLAN 1 on Cisco Router

Hi Guys,

The router in question is a simple RV320. On it there is the following setup:

-VLAN 1 with LAN network, all ports untagged
-VLAN 20 with Voice network, all ports tagged

With this how is the connection to the Switch? Are the ports on the switch on trunk with allowed vlan 20 (and default VLAN 1)?

This is simple but I'm making this more complicated than it needs to be and lost myself.

Thanks!