Right now AppInternals 10 only show HTTP Status codes in Steelcentral Portal via iframe or in the Appinternals UI itself. An exception metric per transaction is possibly the next best/closest thing. Failing that, the metrics for violations are very very useful.(you need thresholds set)
Have you looked at the exceptions and http.status for each transactiontype ? They might correlate or give you what you need.
The Rest API option will show the same metrics that you see in the Portal and UI except the "search" tab(this is raw transaction data).
I'll find out the status of this enhancement request and give some idea on timescales. I do agree that this is a very useful metric, we had it in v9, so it may make an appearance soon!