It is quite likely that the WS-19 and WS-15 engines use similar materials and technological solutions. So there will be some commonality to the design effort of both engines. But we have plenty of evidence that the WS-19 was in fact relatively advanced in design a significant time back.
The J-35, as a naval strike aircraft, is also better served with a twin engine solution since this might enable the airplane to return back to the carrier battle group in case of engine out. Something which is impossible with a single engine. This is much less of an issue with land based aircraft since the pilot has much better chances of escaping alive in case of needing to forcibly ditch the aircraft for whatever reason.
The J-35, as a naval strike aircraft, is also better served with a twin engine solution since this might enable the airplane to return back to the carrier battle group in case of engine out. Something which is impossible with a single engine. This is much less of an issue with land based aircraft since the pilot has much better chances of escaping alive in case of needing to forcibly ditch the aircraft for whatever reason.