Migration from Eloqua to Marketo

Hope you all are doing good! I have delivered a POC on Marketo and its a success, now to evaluate the different Business Use cases I need to recommend Best Application that will give best result while integrated with Marketo. The major Use Case Group I think of are as follows :

-Demand Gen

-Territory Mgt

-Relationship Mgt

- Scoring

-Cross sell/ Upsell

However I am not getting what all questions need to be asked with the Client in order to think in detail for these aspects. What would be the correct set of questions. Please help me with the initial thought process, so that before giving actual SOW we jaunt down all the requirements as well as give best recommendation from my side. For a better idea, just want to tell I do have operational knowledge of Marketo and working with client on business side for the very first time. Any help or guidance will be appreciated. Looking forward for all the help.

Thanks!