I’m looking to add a second camera into my device and am not sure AE3 supports another one in addition to the integrated PAG7936.
No, it only handles one at a time. If you wanted to connect a SPI based camera jpeg trigger you could do so: https://www.arducam.com/arducam-new-5mp-mega-spi-camera-module-with-m12-lens-for-any-mcu.html