The money you get from Project Wonderful is not very good at all. In fact, it's really, really bad compared to Google Ads. You do have a lot of control over the ads, but unless you have a truckload of traffic with click-throughs, you'll make little to no money.
I wouldn't go as far as to say intrusive. You put them where you want them. But unless you have good traffic nobody will pay to place an ad on your site, which means the only ones that show bid nothing. These are (in my experience) things like dating sites, homemade jewelry and the like.
If I see an ad - and I am not there for the ad, it's intrusive.
If they are in any shape or form trying to get my attention that drags my attention away from the content, it's quite intrusive.
If they pop up, over or under, slide out, include sound or annoying animation. It's simply ruining the experience of reading or browsing the content.
But they don't do that. The ones that I've seen sit there in their little box or banner and just stare at you, begging for your attention. I encountered no sound ads, no pop-over or -unders. If the person owning the site puts an ad into a place that detracts from the site then it's not the fault of PW, but of the designer.