The best possible deceleration – minimum landing distance, is with max manual braking and reverse thrust.
With autobrake and reverse the landing distance may be longer. This is because reverse may meet much of the selected value of autobrake deceleration, resulting in a reduced brake pressure.
With max manual braking and reverse, the effect of reverse is additive to manual brake (with autobrake it may only complement it - as #6).
This is shown diagrammatically on slides 10 – 14 in the Boeing presentation
‘Landing on Slippery Runways’.
Depending on the brake system design, the touchdown wheel-lock protection should work irrespective of autobrake / manual selection, although in some types it may be associated with antiskid, but each may be separate, independent, functions.
Check the small print on advisory landing data charts whether the distance data assumes manual or autobrake ; e.g. third bullet on side 14, Boeing gives both for normal ops (slides 6/8) – but check again for abnormal configurations.
An old copy of a 737 QRH for flapless landing states “Assumes maximum manual braking and maximum reverse thrust when available on operating engines”. Also that the assumed air distance from TCH to touchdown is 1000ft; this is unlikely to be achieved, even more so if a shallow/flat approach is flown.