doesn’t seem like 18ga would be adequate. Everything I’m reading online starts at 14ga. for a 15amp circuit. My guess is that wiring is for a DC low voltage circuit. You said you were looking at the wiring diagram of the home, does it not tell you what these wires are for? Have you tried to put a voltage tester/meter on them?
If you read the instructions for installing the wired spotlight cam, it comes with a cable. I would imagine its got a plug on it. You would need an outlet to plug it in to. This would require three wires, a hot, neutral and ground for 115v AC (assuming you are in the U.S…you didnt tell us). Were you planning on hooking the other end of those 2 18ga wires to a breaker or something?
This is probably why you haven’t received an answer. Best I can tell the wired spotlight cams are not hardwired in the first place. If you watch the video in the installation instructions, it clearly shows the guy plugging the cord in to an outdoor AC outlet/plug.