Only the person streaming the game needs the blue box ticked off (This will hie the ingame UI/HUD)

If, casters and observers would like to use BLOB's overlay ontop of their game, the party leader can tick the blue box for them aswell

What is the difference?

The Blue square is responsible for hiding the HUD. So whoever is streaming the overlay to thje stream… should always have this ticked on.

It is optional for everyone else in the observer slot unless they want to have BLOB's overlay ontop of their own game to use.

The grey box is to give moderator perms to that user without the rest of the lobby having access to cheats. - E.g. spectating players, freecam (flying around), sight lines, seeing through walls etc. - This is necessary for EVERYONE in the observer slots