To my understanding Boeing MFRH is >400' agl, but for training purposes they suggest 1000'.
I have not suggested engaging A/P below company MFRA, usually company minimum 1000'agl.
TOGA is a speed mode not an attitude mode. On take off that speed will depend if you have an engine failure or not, and at what speed the engine fails. The MCP window stays open. On SE engine G/A the FD is initial pitch and then MCP speed which is Vapp. The window stays open. On normal 2 engine G/A the window closes and speed bug is F15 speed for MTOW. This is a higher speed than necessary for given ALW F15. Engaging A/P with MCP wind closed, it then opens MCP window in no worse a climb gradient than you had before. By retracting flaps >400' in automatic speed mode, the a/c will reduce attitude to accelerate and reduce ROC. This may happen before you are clear of obstacles, but is a Boeing procedure and adopted by some companies. Where does the raw pitch attitude command come from?
By engaging A/P at 1000' on 2 engine G/A allows PF to bug UP the same as a normal takeoff. Then PM can retract the flaps in a calm manner as you do every day. By observation, in the sim the biggest screw up of a normal manoeuvre is 2 engine G/A, when it is done different to a normal takeoff. When done in the same manner that is not the case.