I may be wrong, its a while since I flew the 800. But surely a second push on the toga during the takeoff ( 80 kts to 800')does sweet fa to the thrust. ground logic, you are in takeoff , not go around. It may adjust the carrot or give you the fd's back after 90 kts but Im sure thats about it. The thrust levers are in hold at 80 knots until 800 feet , then arm I believe.
After 800 feet and arm, i dont know . depends if take off mode (vis vis thrust) is a speed/pitch mode or an n1 mode or not. Cant remember. That is to say it will stay armed (pitch/speed) until another mode (n1/a/p/lvlchange/alt cap etc) is chosen or happens. pretty common boeing thing. 75/76 has no thrust mode until chosen after arm fma ie alt cap does not default to an epr/n1 mode as i beleive it does on the 800 , hence the low level early cap issues and runaway speed due to no thrust mode control.
oh I dont know, back to the wine.