Do covert ops, like Anathema, etc, ship's sensor types have any effect on their ability to scan down sites? Is a ship with radar sensors able to scan down radar sites more easily than gravimetric or similar?
It's a bit misleading, but sensor strength of your ship has nothing to do with how well you can scan down anything. It affects two things:
The important parameter for scanning is the sensor strength of the probe (which isn't classified as gravimetric, ladar, radar, ...), and there are several factors that can increase this: