Why does the Torah not tell us what they did with the gold, like it says about the silver and copper?
Ramban (on Pasuk 21): Because it was not known exactly how much gold went into each of the K'lei Kodesh, which were all under the jurisdiction of Elazar. 1
Riva (21), Hadar Zekenim, Da'as Zekenim: The only full Kelim made from the gold were the Menorah and its Kelim, they were a small amount 2 (one Kikar). Almost all was to plate the Kerashim and other Kelim.
Tosfos ha'Shalem (27:2, citing R. Yehudah ha'Chasid): It is impossible to weigh metal plating attached to wood.
Why does the Torah list five kinds of gold Kelim - Choch, Nezem, Taba'as, Kumaz and Kol Klei Zahav?
Moshav Zekenim: These corresponded to five kinds of afflictions in Egypt - Parech, Merer, Inuy, Lachatz and Avodah Kasheh.