Can someone please suggest few best approaches for A/B Testing for triggered or real time email campaigns (continuous or recurring deliveries) in Adobe Campaign Classic.
A/B testing should just be part as usual of the repeating workflow for repeated deliveries.
I would suggest you run your own test to see if you'll get the desired results.
I hope this helps!
All the best,
Transactional A/B testing is best done by the caller or an intermediary.
It is possible to do in Campaign with some sleight-of-hand, using a workflow to swap published templates every x minutes while synching/counting logs to determine a winner past a threshold, though this is not ideal.