What should I think about while setting up AA that I might need for CJA?

Hello, Adobe recommends this linked implementation path for the follow circumstance:

• You intend to use Customer Journey Analytics in the future, but do not want to replace your Analytics implementation with a Web SDK implementation from scratch...

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Another callout:

If your organization plans to use your own schema with Customer Journey Analytics in the future, use of the Adobe Analytics schema can create confusion for data admins or architects.

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By using the Analytics Data Object you can avoid using the Adobe Analytics schema. This will require work down the line to map the Analytics Data fields to the corresponding XDM fields. 

Alternatively, the below is advised as the "best" CJA path but not sure how practical it would be for most AA users. 

• You can skip the Adobe Analytics implementation entirely, and send data to Adobe Experience Platform using your own schema. This approach is ideal long-term, and allows your organization to start using Customer Journey Analytics.

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Hope this helps!

I think you are already on the right path by moving into Edge network. 
Make sure you read this article - https://experienceleague.adobe.com/en/docs/analytics-platform/using/cja-data-ingestion/ingest-use-guides/edge-network/aepwebsdk

This highlights all the needed steps you need to make sure for the schemas in AEP. 

Also there is a webinar on May 30th that you can register to understand the critical implementation steps. 

Thanks