Ideally, we go for change request if a change has to be made to the existing functionality/system and needs to go through the infrastructure level approval to assess the risk & impact associated with the change
Request management is used when the process had defined steps of fulfillment like providing access, processing data etc.,
In order to store the data of approvers for each role, you need to create a custom table. Amd whichever approach you picked up from above two options, you can query this custom table to get the list of approvers to create approval request using ' ask for approval ' activity in the flow designer.
For these type of scenarios, I would suggest to create table using data lookup rules because this type of table will not attributed to custom table count.
https://docs.servicenow.com/bundle/xanadu-platform-administration/page/administer/task-table/concept...
