And reduce the function size to simplify

_123, -123, _-12, __-1  plus  1234, 12.3, -1.2

- This function becomes obsolete if ftostr4sign is re-written.

Unlike RAM-based strings, PROGMEM strings aren’t consolidated by the
compiler.

Added all missing strings according to English

Follow-up to #5330

Grammar corrections

・Update forgotten Configuration_adv.h of Felix\DUAL and K8400\Dual-head

・Make descriptions the same as others

to capture chars at UART at 250000 baud.

.. and give the hint to try lower values if possible.