Just curious as to why the tabs at the top (Home, Boards, etc.) moved from being centered to left aligned...not a big deal but I'm discovering how trained I was to them being in the center .

This is in preparation for the game clock changes - the game clock will go on the top right of your screen.

Will the game clock apply only to a game open in the window or will that area support multiple games?

It will just apply to the game in the current browser window.