For the Cardon system you will find the info on page 4 here.* You are correct that you will need to thin out the clusters as overcropping will result in poor fruit quality.
More info here on Cordon if you scroll down.
Does that answer your questions?
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.