Does New South Wales have a longer coastline than Tasmania?

No.

The mainland coastline of New South Wales is 2007 km in length, while the islands make up an extra 130 km of coastline length.

The mainland coastline of Tasmania is 2833 km in length, with an additional 2049 km of coastline on its islands. This gives NSW a total coastline length of just 2137 km compared to Tasmania's total coastline length of 4882 km.