Chris Wollman posted a 6-under-par 66 at Cliffs Valley and is alone in fourth place.
The format features each player joined by an amateur partner or a celebrity, like the AT&T Pebble Beach National Pro-Am on the PGA Tour. The 14 lowest-scoring teams (seven pro-celeb and seven pro-am) advance to play in Sunday's final round.
For the first time in Nationwide Tour history, play is spread throughout three courses over the first three rounds - The Cliffs Valley Course at the Cliffs Golf & Country Club, The Cliffs at Keowee Vineyards and The Cliffs at Walnut Cove. The Cliffs Valley Course is a par-72 layout, while the other two are par 71s. The Cliffs Valley Course will host Sunday's final round.
All three leaders played Keowee Vineyards on Thursday.
Armour mixed three birdies and a bogey over his first nine holes, but his play on the back nine vaulted him to the top of the leaderboard. He birdied 13 and 14, then added an eagle at the 15th. Armour closed with a birdie at the last to match the tour's lowest nine-hole score this year with a back-nine 30.
'The biggest thing for me today was that I didn't miss a fairway,' said Armour, whose 64 equaled his lowest career round on the Nationwide Tour. 'I hit all 14 which I haven't done in maybe two or three years. When you hit all 14 of them, you can be aggressive at flags no matter what distance you have in.'
Hoffman opened on the back nine and broke into red figures with a birdie at the 11th. He collected four birdies in a five-hole span to polish off his opening nine and, like Armour, tie the tour's 2005 record for lowest nine-hole score.
Hoffman only tallied two birdies on his second nine, but the 28-year-old still managed a tie for first. He did it the same way Armour did and hit 12 fairways on Thursday.
'I drove it real well today,' said Hoffman. 'I don't think I missed a fairway with my driver. For me it is the key any week because it seems if I can hit it long and straight it helps me out.'
Mills mixed five birdies and an eagle for his flawless round.
Aaron Barber, Mathew Goggin, Chris Kamin and Jerry Smith share fifth place at 5 under par.