I thought that Eporius was Greek. I am well aware that the Macedonians were merely Hellenized. My uncle is married to a Macedonian.
At the time of Alexander, the Macedonians spoke a Hellenic language fairly closely related to Greek, but not readily intelligible to "real" Greeks. The Macedonian royal family and aristocracy were becoming increasingly hellenized.
Epirus was an even more backward and remote region. Its inhabitants were probably a mixture of primitive more or less Greek-speakers, similar to Macedon, and Illyrian (probably ancestral to Albanian) and Thracian tribes. It was considered even by the Macedonians to be barbarous, one reason Alex's mother was never popular with the Macedonians.
One of the nastiest squabbles of the last century or so is the issue of who "Macedonia" belongs to.
The Greeks claim it on historical grounds, a big reason they're so territorial about Alexander. They claim he was Greek, and he was from Macedon, therefore Macedonia must be Greek.
Meanwhile, most of the actual Macedonians speak a Slavic language more or less midway between Serbian and Bulgarian, causing both the Serbs and the Bulgars to claim that Macedonians are "really" Serbs or Bulgars.
At the moment, it appears that the Macedonians are opting out of this three-way tug of war and going for independence. Let's hope it sticks.