"set climb thrust bug up"
Not sure what this means. Never heard it and can not desypher it. After N1% the thrust will be in CLBnot TOGA. TOGA is a pitch mode for speed control. If you are accelerating to climb speed to go en-route it would be normal to use VNAV after flaps up. I did hear an opinion that TOGA pitch mode, when used to accelerate, was about 40% accel & 60% climb, whereas LVL CHG was 60% accel & 40% climb. Like I siad this was an unsubstantiated opinion. You'd have to ask a Boeing Test P. However, once these 'opinions' get around they become fact. I never heard any opinion about the ratios in VNAV. However, you are talking of seconds over a normal flight, so anyone thinking they are making a big difference is deluding themselves. If they want to accelerate fast use V/S.