SAP S/4HANA 1909 Conversion - Simplification Items and Finance Functional Consultant activities

Hi Experts,

This is sort of a generic question regarding S/4HANA conversion from an existing ECC system. I have just started in this journey and have a few basic questions, so please pardon if its too obvious or basic a query.

In the journey to S/4HANA in a brownfield project, I know that its broadly two phases - Prepare and Realize. In Prepare phase, there is the Planning, Readiness Check 2.0 (against the simplification catalog), Maintenance Planner, Custom Code Migration (incld cleanup) and cross & application specific activities. Where in the Realize stage its the actual system conversion with the SUM with activities of DB Migration, Software Update and Data conversion, followed by some cross & application specific activities.

After we upload the system details in the new Readiness Check 2.0, SAP lists the relevant Simplification Items and activities related to those simplifications that we need to perform.

Now, my first question is that as a functional consultant in finance, I am trying to understand what are the activities that I actually need to perform in this conversion wrt the simplifications and also during and post conversion, from a perspective of configuration, design, etc? Some of the simplification items (categorized as customizing by SAP) that I checked so far are mostly pointing towards custom code checks. Most of the activities I can see till now are either Basis or ABAP related. From a functional end what are the tasks that I need execute? Are there simplification items that a functional consultant needs to manually configure in the system? Other than the simplification items, what are the other items/activities in a conversion project that a functional needs to work on?

Also one more question, wrt simplification items, is that there are some mandatory simplification items that are pointing to modules that are now no longer used in our client's system, for ex: Real estate classic, which is no longer in S/4HANA. This module is no longer used in ECC in our client's system, but there are some data traces in tables from history, that are still there in the system. In such cases, do we need to work on such mandatory actions to convert to S/4HANA, or can we just ignore them? Will ignoring corrections to such unused items later create a technical roadblock during the conversion?

Please advise!

Thanks & Regards.