Gold is much easier to counterfeit. You can have wolfram-lead bars coated with a thin gold outer layer, by weight they would be the same if mixed correctly.
Only a specialist with ultrasound can detect the scam. Of course if you buy the gold from a reputable dealer the chances of getting scammer is low.
But if you buy it from a shady local dealer, then it might happen. Thousands of people get scammed by this worldwide.
You seem to be very unfamiliar with the gold trade. If you buy gold in "bulk", i.e. non-standardized gold bars, and from a shady source, you can always drill the gold ingot. Gold is soft while tungsten is one of the hardest metals out there (twice as hard as steel), and you would need a special drill bit to do the trick (that is, to drill through a tungsten bar)...
Yes.
I buy 1 oz gold coins (US Eagles). Au Eagles have 1 toz of (24 kt) gold as well as some Cu and Ag to make them sturdier. Still there are fake 1 oz Eagles out there made of tungsten, I recently watched a YouTube video on some fakes that fooled the buyer at a coin store (until the owner or expert got a GOOD look at them). One oz Eagles are also less "profitable" to fake, but apparently they ARE out there. I have never seen one.
Also, Gold Eagles have a very clear & beautiful "ring" to them, balance one on your fingertip and strike it lightly along the rim with a quarter. The ring goes on and on, very satisfying.Tungsten just makes a click/thud kind of sound.
The above "ring test", along with a scale that weighs to 0.1 gm (so a Gold Eagle weighs about 33.9 gm) is enough to catch them all.