I am planning a couple projects and wanted to take advantage of the camera component, and got the device below. That said, as I continue looking it looks like the I2C pins are internal to the board, which would make hooking up other I2C devices. Am I reading the schematic wrong or can I not use the I2C bus on the chip for other things? Can ESPHOME have multiple I2C buses defined?
Correct. Pins for GPIO21 (SDA) and GPIO22 (SCL) are not connected to the header pins. You would have to solder directly to the surface mount pads of the ESP module to add extra devices.
No, it uses the internal i2C hardware and associated registers. No software based i2c is available. So only one bus on the pins specifically associated with the i2C bus.