For FE Hopper re the bank angles commanded by the system, from the FCTM 3.31
"The AFDS limits the bank angle to 15 ( deg) until V2 + 10 knots to maintain at least adequate maneuver margin. The bank angle limit increases to 25 (deg) by V2 + 25 knots if LNAV is engaged, or when HDG SEL or TRK SEL is engaged with the bank limit in AUTO"
As a rule of thumb, 1 or 2 engine, Man speed for the flap setting you have will give you 40 (deg) of bank capability (25 +15)
V2 +15 will give you 30 (deg) 15 + 15)
Flap retract speed, ie man speed for the previous flap setting same as V2
As to the original question, I agree that if you do no need the extra power on an ATM T/O then leave well alone. But if you do or think you do then the easiest way is to push them up slowly and then hit TOGA (or not) If you do not hit TOGA then the power will just come back when VNAV engages, bit messy if TAC not working but you should have the AP in by then. You get the extra power for the most critical period and no hassle.
FCTM is very specific re increasing power during fixed derate, "ONLY if terrain contact is imminent".
Be careful out there, watch out for gravity, it will eventually win