The Theravada position is a lot like the Sautrantikas, but not the Vaibhasika / Sarvastivadins.
This Theravada / Sautrantika position is in turn similar to, but not identical with, the basic Madhyamaka.
However, the Madhyamaka, especially if it is read through Mahayana sutras (which is almost always the case) has some other ideas, besides.
All are "illusory" (like illusion, mayopama), but they don't quite mean the same thing.
Likewise for "empty", too.
My recently moved Blog, containing some of my writings on the Buddha Dhamma, as well as a number of translations from classical Buddhist texts and modern authors, liturgy, etc.: .