What are the differences between the insolvency monitor (Sachwalter) under the ESUG and the restructuring officer under the StaRUG?

Under the ESUG (the German act facilitating the restructuring of companies), the insolvency court always assigns an independent insolvency monitor (Sachwalter) to the company. Under the StaRUG (the German Act on the Stabilisation and Restructuring Framework for Businesses), the appointment of a restructuring officer is in some cases mandatory, in some cases optional and in some cases not required. Unlike the insolvency monitor, the restructuring officer is not remunerated under the German Insolvency Remuneration Ordinance (Insolvenzrechtliche Vergütungsverordnung), but according to the actual hours worked.