Can meeting organizer change all participants' video layout?

I am hosting a meeting in which I would like my 3 speakers spotlighted, and I want to share a screen at the same time. BUT, I only want my screen share window to appear as large as my 3 spotlighted presenters appear (so imagine a square divided into 4, with three of those divisions being my spotlighted presenters, and one of them being my shared screen). 

I don't want to use webinar mode, because I'll need to send everyone off into breakout rooms once the opening speaker presentation is over. 

So my question is: I understand that each individual participant can change their video layout on their own screen to make the screenshare window smaller. But is there a setting that allows me as meeting host to override their individual settings, and make the screenshare window the same smaller size for everyone?  FYI-we have a pro account.