Is it relevant to the game ?

like yes, but you shouldn't worry too much about it, just keep these in mind: estuary good, these are provinces that give a lot of trade power in a node they have a lil icon when you are in the trade view, you can upgrade them for a lot of money. Having more trade power in a node means you make more money out of that node so if you collect there you will make more money, transfering trade power is good if the node transfers to your node and you are colecting there already, if a trade node has a lot of money and you have light ships you could privateer and make some cash and that doesn't even use a trader, or you can use them to give you more trade power on your trade node or a trade node you are transfering from so you steal more money from there, that is pretty much all you need to know without going way too much on how it works, like there are also end nodes, in vanilla they are geneva and venice and the one under england, and they have no place to transfer and that makes them great because no one can steal money from there, so those are generally really good to be pirating or conquering, also republics are better at trading and some countries are better at it , it depends on the ideas and special government stuff, but like it is fine, you really don't need to make the most of it unless you really want to steamroll the ai