Trading in Multiplayer Games with the Definitive Edition

I wanted to ask those who play online using the Definitive Edition, what happens exactly with their resources when they trade. I used to play this game offline many years ago. I remember that when I traded, as a seller, with another player (AI), I earned gold but I had to give either food, wood or stone in every trip to that player's dock. I wonder, the human players who trade as buyers: do you receive different amounts of food, wood or stone? or always the same regardless of the distance from your docks? And what happens if you run out of gold because, for example, you have exhausted your goldmines, can you continue trading?

If trade is bilateral, what are the advantages and disadvantages in the game and your recommendations in multiplayer games? What if one player has, four trading vessels and his trading partner only two and they have only one trade route?