I have a question regarding using a gold tile hex for gathering resources and commodities.
For example, if a gold tile is used for gathering resources and commodities in the game, and a player has a city next to it, and the right number was rolled on the dice, if he wanted wood as his wild card choice, would he receive both a wood resource card and a paper commodity card? Or because since he has a choice, can he take just two wood cards if he wanted wood?
Unless you are playing a variant which has a commodity for gold hexes (there are a few), gold hexes in Seafarers produce only resources, never commodities. A city will yield two resource cards of the player's choice, which don't have to be the same.
If you are playing C&K with E&P, gold hexes produce gold coins (2 per settlement or harbor settlement, 4 per city) rather than resource cards).
Commodities aren't available from the bank for gold coins, only resource cards.
Tactically, having another option to get resources that have become rarer because of commodities coming in is desirable in a game of C&K.
But these combinations are of course already variants that don't really have official rules, so you can create a variant or house rule that does have your choice of a commodity if you have income for a city on a gold hex.
You might just as well designate another type of hex - e.g. the desert hex - to get a number chit and to produce a commodity (only) if the number is rolled and you have a city on it. A settlement on a desert wouldn't earn anything.
Depending on your victory point target and other sources of victory points, getting commodities can become meaningless in the later stages of the game when the metropolises are permanently assigned and commodities have become mere 2:1 trading assets.