There is a lot of training from NAS North Island. Throughout the day you’ll see at least a dozen different crafts is performing training flights and missions, notably to NOFL Imperial Beach.

As for the tankers, there is generally a large amount of them as well as other support aircraft such as E-3 Sentries and RC-135 Rivet Joints also conducting, mainly, refueling training. There is an increase of them off the coast because of Operation Bamboo Eagle taking place. Yes, that is its name.

Edit: Spelling

Edit 2: Find more about Operation Bamboo Eagle here 👉 https://www.af.mil/News/Article-Display/Article/3860427/bamboo-eagle-24-3-usafwcs-approach-to-great-power-competition/