Quietest times for breakfast are the earliest hours. Busiest are 9:00 am onward to the close of breakfast time.
Lunch is usually served at TS until approximately 4:00 pm (sometimes 3:00) when it changes to dinner time. Dinner runs until approximately 10:00 pm for TS (or until park closing).
Counter service will open depending upon the food served there. EPCOTs many counter services of the WS are not open until 11:00 whereas the breakfast in Norway is open much earlier.
There are CS places open at 9:00 am at FW, but not all FW CS is open when the park opens.
Hope that isn't too confusing!