The diameter of earth is a bit more than 12600 km. The height of the highest mountain at 8.9km above sea level, is therefore about 0.07% of the diameter of earth.
Billiard balls (apparently) have different sizes, but let's assume 60mm in diameter on average, or 0,06m. 0.07% of that is 4.23*10^5 m or about 42 micrometer.
So an accurate copy of earth at the size of a billiard ball would have Mount Everest being 42 micrometers high.
The circumference of earth is about 40000 km. The Himalayas (which are on average Very Large© mountain) are about 2400 km long. But it is curved so let's say 2000 km. That's about 5% of the circumference of Earth.
5 % of 60 mm x π is a bit more than 9 mm. So let's say it has a bump that's 0.03-0.04 mm that's 9mm long. No idea if that's the smoothest billiard ball ever, but it surely would be very smooth.
And the Mariana Trench is about 11 km deep, so not much deeper than the Everest is high. Let's say 0.05 mm deep. Would even an average size drop of water fit in the entire oceans?
This all assumes my quick math wasn't completely wrong... I did it while waiting for a patient who seems to have forgotten our appointment...