We were out there in 2017, and did the Rte 132 loop around the peninsula, and it has changed a lot. No more all day Walmart parking. 23:00 to 06:00 only.
As for campgrounds, I don't recall seeing a lot of them, but we didn't use campgrounds much back then in a Class B Van. You could always find a place to park for a few hours of rest, or overnight. Not so easy any more.
There are a few National Parks that might have camping, Parc National du Bic is nice but crowded. We've used it for showers.
This map shows what's out there at various degrees of zoom. More smaller ones show up if you zoom in a bit.
https://www.google.com/search?q=rv+campgrounds+around+the+gaspe&npsic=0&rflfq=1&rlha=0&rllag=48873051,-64363719,9758&tbm=lcl&ved=2ahUKEwiVrNG09u7iAhUmx1kKHQYZBjwQtgN6BAgKEAQ&tbs=lrf:!2m1!1e2!3sIAE,lf:1,lf_ui:1&rldoc=1#rlfi=hd:;si:,48.74013791423887,-67.33256465484106;mv:!1m2!1d48.43217282623323!2d-68.48019238392135!2m2!1d48.23406040500562!2d-69.0707075206401!4m2!1d48.333212833392835!2d-68.77544995228072!5i11 Can't recommend any, because we used them sparingly when we used to go out there.