Material: wood, stone will do.

Font: Official script is widely used. Seal script is also often seen.

Typesetting: No matter whether it is horizontal or vertical, there is generally no stress.

Engraving and three-dimensional printing, do you mean whether the characters are convex (male) or concave (female)? If so, it should be the kind that can stand out from the crowd. Generally, two seals are not required. But in Japan, stamps are used in many places, so it doesn't hurt to prepare one more.

Even if you carve two, there are no other special rules on size, material, font and typesetting.