He generally takes a lot of long-distance shots (over 60% of his shots for his career) and he's really only been scoring them the past two seasons (5 this season, 4 last season). He has 3 goals inside the penalty area this season, an improvement for him, and maybe a better team can generate better shots for him (his 2nd best goalscoring season in a "big" league was Bayern 13/14, where he took more shots inside the box than outside) but I always worry about regression to the mean for players who consistently take low-quality shots. There are really only a handful of players in the world who score them consistently.
In terms of chance creation, he's played over 2 key passes per 90 for his career, most of which WhoScored classes as "short" passes. With that said, when sorted by pass type, most of these chances seem to be created via set pieces and crosses. It's hard to say much about this without access to better data. WhoScored is the best I can find but their numbers don't always add up, which is obviously problematic.
According to WhoScored's style of play descriptors, he "likes to play long balls," "plays the ball off the ground often," "likes to shoot from distance," and "likes to cross," all of which sounds accurate based on those numbers and what I've seen from him and almost all of which sounds perfect for Allardyce (who cares about shot quality and generally discourages shooting from distance).
He's a pretty good Premier League winger but my general feeling is that we should be doing better, especially if we replace Allardyce with somebody more progressive.