can you track your apple watch if it’s dead?

Unfortunately you can't. You'll have to wait for it to be turned on before you could track it.

What you can do for the moment, if it's lost, is to place it in Lost Mode so that you'll receive a notification when its location becomes available.

If your Apple Watch is lost or stolen - Apple Support (MY)

No. It has to be powered on and connected to the internet for Find My to work. After it being dead for a while, if you try tracking it again, it will eventually start showing it as being located where your iPhone is. That is because it will be tracking your iPhone. Because the Watch is paired to the iPhone and Find My works for both devices, when it can no longer track the watch because it is dead, it tracks the phone because of the pairing.