Is "Get Player Controller" always needed?

i’m creating and learning about widgets and huds, when i have
“Create … Widget” do i need to set “Owning Player” as “Get Player Controller” or is it okay not using “G P C”?

Yes, if you try compiling the blueprints and a node requires the GetPlayerController then it will give you an error.

When i do something in the ThirdPersonBP (self) is GetPlayerController right?

No you technicly dont and it will Compile just fine.