During my conversion to the 787 at Boeing they emphasised not to increase power past the fixed derate in the event of an engine failure on takeoff. However, they also suggested that once the speed was more than 149kts VMCA was not a problem.
They also never mentioned the 12 degree target attitude after an engine failure but rather stressed to pitch to the TOGA Reference Line in the HUD which would always be correct. Experience would suggest that they were right.