I am not an expert on the two subjects to even suggest anything here but it's a very good question and I couldn't stop thinking about it. So I thought may be I could point to some Kbs here that I have seen on this subject.
There are a few limitations to point out wrt AWS outpost:
• Only single node Cloud Volumes ONTAP systems are supported at this time.
• The EC2 instances that you can use with Cloud Volumes ONTAP are limited to what’s available in your
Outpost
• Only General Purpose SSDs (gp2) are supported at this time.
AWS Outpost limitations in Ontap 9.1.1:
http://docs.netapp.com/us-en/cloud-volumes-ontap/pdfs/pages/reference_limitations_aws_991.pdf
AWS outpost & netapp:
https://cloud.netapp.com/blog/aws-cvo-blg-netapp-achieves-aws-outposts-ready-designation
https://docs.netapp.com/us-en/cloud-volumes-ontap/reference_limitations_991.html#unsupported-ontap-features
AWS compute, storage, database, and other services run locally on Outposts. Outposts is available as a 42U rack that can scale from 1 rack to 96 racks to create pools of compute and storage capacity. Coming in 2021, Outposts will be available in two smaller form factors, 1U and 2U rack-mountable servers for locations with limited space or capacity requirements.
https://aws.amazon.com/outposts/
I guess, when it comes to Flexpod we are talking about compute/storage/network all stacked in a pod with pre-configured capability and so will the AWS outpost-racks will try to mimic. However, I think the key important differentiator could be that the 'flexpod' at your premise is still a on-premise well known ONTAP. However, in AWS it's all about the CVO (Single or HA Pair). I am guessing, more than the performance it may be down to the high availability of CVO (HA Pair) to ensure the uptime of mission-critical applications in the AWS outpost from "data serving function" perspective.
CommVault has a good post around the data protection on AWS outpost:
Reference Architecture of AWS Outposts:
https://documentation.commvault.com/v11/essential/130468_reference_architecture_of_aws_outposts.html