Wazup dude... sorry for the l8 reply to your question (hardly on the forum these days)
"In GKT, the column "competition" is about Adwords competition. Right ?
Would that metric only apply to the search network or can be applied to the CTT network ?"
Good question! Yes, it is reflective of adwords comp. but it is virtually impossible to tell from that metrics how many of the advertisers are actually bidding for ads to appear on the content network.
However, what you can do is type in your keyword into Google's search engine and visit a site that displays Adsense ads... on that site you can gauge how many relevent ads are showing in relation to your keyword. This is a good method to determine the comp. amongst adverisers bidding on the content network.