Musings on Normandy

[CheerfullyInsane]

Also approach the BB boats as much as possible, since I understand that with a closer approach to the beach it improves the impact against the bunkers

Nope, range has no effect on the fire-values of artillery.
The only exception is the close-range Hard attack modifier in the PDT, but that only applies to artillery using Direct Fire at a range of 1.
So you'd have to run the battleships onto the beach itself in order for it to have any effect.
Granted, after the beaches have been cleared the Navy should move in in order to increase the range inland.
But it doesn't have any effect on the invasion itself.