The layout for Micro ATX vs Micro BTX is mirror image.

Optiplex models have been around for 27 years now.

Dell does not publish pinouts for front panel, thermal sensor, fan headers etc.

There is no such thing as one size fits all for Optiplex or any other series like XPS or Inspiron etc.

BTX or Balanced Technology eXtended is a form factor of the motherboard that was introduced by Intel in 2004. It was designed to replace ATX.  The micro versions have 4 slots instead of 7

Spec	Year	Dimensions	slots
BTX	2004	10.5 × 12.8 in	7
microBTX		10.5 × 10.4 in	4
nanoBTX		10.5 × 8.8 in	2
picoBTX		10.5 × 8.0 in	1

Size	ATX	BTX
Full-Form	ATX stands for Advanced Technology eXtended	BTX stands for Balanced Technology eXtended
Meaning	ATX is a form factor of the motherboard which was introduced to replace the standard AT design.	BTX is a form factor of the motherboard which was initially designed to replace ATX.
Invented	ATX was first introduced in 1995 by Intel.	It was introduced in late 2004 and early 2005 by Intel.
Airflow & cooling	ATX board design and component location block airflow. Thus, less cooling.	BTX solved this problem and has better airflow, hence more cooling.