Will any of the features from Stream classic not transfer over to Stream (on SharePoint)? Will I still be able to upload a video to Stream and have Stream auto-generate a transcription for it?
Stream on SharePoint offers the same features as Stream Classic with many improvements. However, at this time the ability to add embedded polls to Stream videos is not currently available in Stream on SharePoint. Microsoft has included this feature in their roadmap and has indicated that it is in development. We will update the community re: release date as we know more. Improved auto-transcription is available in Stream on SharePoint.
You can see a full comparison list of features here: https://learn.microsoft.com/en-us/stream/streamnew/features-new-version-stream#detailed-feature-comparison-to-stream-classic.