Hi @ildomandatore,
From what I can see in the documentation from Google here https://support.google.com/adsense/answer/9274516?hl=en you should only place the code in the header – in WPCode it’s the Site Wide Header location or the Header in the Global Header & Footer area.
If you are using automatic ads placement you might not have to place another code on the page. If you want to place individual ad units you can add those using snippets and place them where needed.
Regarding the performance of the ads that’s handled by the way the ads are loaded externally and it’s not something you can control from WPCode since the script is loaded from Google’s services.
Yes, I have set the automatic insertion of advertising. I don’t know if that’s a good thing. I’ve followed their guide in the past and it said to put one code in the header, the other in the footer.