What base should I implement for game logo, patch, lobby screen UI switching?
Should I set the game mode for each level and add widgets to the viewport in the game mode?
Or should I work on the level blue print?
Hey @voidpeople!
Typically this stuff is widgets added to viewport in the level BP. You CAN use game mode for these things, but you wouldn’t be able to use it for clients in multiplayer. Hope that helps! 
Thank you.