I've done that and no, it doesn't stop the unwanted apps from ever running. If it did, then my Nexus 7 wouldn't exhibit the thundering herd of google crapware slowing the tablet to an unusable crawl every time I enable WIFI.
How do I know it's Youtube or whatever running? Because Youtube (etc) pops up dialog boxes complaining about timing out or running out of RAM or other resources. (BTW, clicking "OK" rather than "Cancel" is the right thing to do at this point because "Cancel" apparently means "Exit and re-start whatever the fuck you were doing from the fucking beginning", not the expected "Fuck off and just fucking die"...making things worse and extending the period of unusability by another 10 or 20 minutes).
This shouldn't happen. I never run Youtube on the tablet. Ever. I never run Google Maps either (i use OSM when I need a map). I've disabled them. I'm not allowed to uninstall them (on my own fucking property!), otherwise I would have done so long ago. They shouldn't be running at all. So, it shouldn't happen. But it does. Every Single Fucking Time that I enable WIFI on the tablet.