The bag checks: The attendants will ask the visitors to open their bag and just look into it, don't open it by themself or touch it. If someone does not cooperate they won't be let in. They will not check every single bag, but randomly choosen people will be checked.
No attendant is allowed to initiate body contact but can defend himself if someone else touches him. So when someone tries to get in and touches an attendant he may hold and stop him.
I find it remarkable to slow the entrance process down, so people will have to wait many minutes in line. In the last years lots of witnesses are very impatient to get into the stadium. Some get very angry and start to curse against the attendants. This change will make it worse. But of course it is necessary.
My information is about conventions in Europe. Some take place in stadiums but will be less public than in the past. It's less about "real security" but about "felt security".