Player logged in appearing in middle of the screen

[Nikisndrs-kelthuzad]

This thread had a fix for it. I do not use toasts so cannot guarantee it works.

Friend online/offline alert in the middle of the screen

This appears to be the “Show Toast Window” option at fault. Cr42yC4r1 in the WowUIDev discord shared that you can run /run BNToastFrame:SetPoint("Left",0,0) to fix it temporarily. Alternatively, you can uncheck the option in Options → Gameplay / Social → Show Toast Window. That said, that didn’t work for me strangely, but disabling both “Offline Friends” and “Online Friends” did. Maybe the Show Toast Window option requires a game restart to take affect - I couldn’t test this at the time.