Armstrong is the very definition of a mercurial winger, for this level. It's a cliché, but it often felt like you could tell how he'd get on in game based on the first thing he did.
When his tail is up he's more than comfortable going either inside or outside his full back, and there are times when you'd struggle to tell which is his stronger foot. Equally, though, some games it just seems like his range is off and every time he tries to play a ball more than ten yards it veers wildly away from its intended target, and he really needs sat down, recalibrated and tried again the next Saturday.
I don't know that he'll ever really find true consistency, not at Championship level or above. If anything, I think you could clip his wings and he'd lose that spark that makes him so dangerous.
He's best utilised when he can go out and play, and the other players around him can get by even if he doesn't perform perfectly for 90 minutes. It's a big ask, and pretty much why he never got a look in at Ross County, but if you can afford it, he pays dividends more often than not.