DO you have a link for the same? I think ive practically almost read everything on this troubleshooting section of Blue Iris now!I don't know, try disabling 3/4 of the cameras and see if you can get it to run with 5-10 cameras. Since it's an 8th generation Intel chip you should read the thread that has info on the Intel memory leak.
Anyone running 8th gen Intel without memory leak problems in Blue Iris?
As @smiticans said above, here's direct link, follow exactly : The Quick Sync Video Memory Leak: 8th Generation (Coffee Lake)
Did you set the live preview setting?
This means you have turned on the "Limit decoding unless required" feature on most or all of the cameras, and that is the only reason your CPU usage is manageable. If you had been doing this two or three months ago I would have told you that you can't do this and still use the web server, because that "limit decoding" setting gets temporarily disabled for every camera being viewed through the web server and the first thing the web UI does is load the All cameras group. You've seen the result of that.