He is right, after the game starts the launcher is not even present. I bet you get the same problem if you run eu4.exe and stellaris.exe by themselves.I don't think it's anything you said. My PC is perfectly and I have no problem with any other game.
I repeat that before the launcher was installed, Stellaris and EUIV worked perfectly. If the problem were in one of the two games, maybe, but it is in both. What is the common point? The launcher
There are many more common points between those games that just the new launcher.
Please pick one and make a new thread in its tech support forum. Thanks.