What does 3 ctw mean for a pair of studs?

It is the combined weight of both earrings, so each stone is roughly 1.5 carats. Actual weight depends on the pair, since stones are matched by weight and size.

Are these good for everyday wear?

Yes, studs are the most practical diamond earring style. At this size they sit higher off the lobe, so check that the backs hold them snugly and that they feel comfortable under headphones or hats.

Four-prong or bezel setting?

Four-prong settings show more of the diamond and let in more light, which boosts sparkle. Bezel settings protect the edges better but cover part of the stone. Choose prongs for brilliance, bezels for durability.

Will near-colorless diamonds look white?

In most lighting they face up white, especially in yellow or rose gold settings. In bright daylight or against white clothing, a faint tint can be visible to a sharp eye.

What should I check when they arrive?

Confirm the backs are tight, the prongs are even and not snagging, and both stones match in size and brightness. Loose stones or uneven settings are the main things to catch early.