When I create a virtual AP interface with the purpose of broadcasting a second SSID do I need to remove my original SSID from the master interface (say wlan1)?
No,
You simply leave that SSID and add the Virtual. You will then have both SSID broadcasting.
Awesome thanks for clarifying! What’s the purpose of VLAN mode over just adding it to a bridge port of the SSID is in ap-bridge mode?