I would expect both AA and CJA Previews to be accurate, as they should be using the API to return data from the last 90 days.
What you need to be aware of, in both AA and CJA, is that the segment is showing data from the correct suite or data view.
The Segment preview is also based on 90 days (not the time frame selected in your panel), and also, any other segments in your panel will not be applied to the segment preview, it will be based on the logic in the current segment alone.
So yes, the numbers should be accurate, but there are caveats based on the what is being applied at the Workspace level (suite, data view, time frame and other applied segments) that will have an impact on the data once returned to your Workspace.
