The way I see it, there are four categories of on-or-off topic posts. I'm no moderator, these are just my common sense inferrals.

Directly On Topic: Something about NASCAR as a sport, or a particular race, or the teams and drivers in respect to the sport. Things like a track repave, a rule change, an incident on track, a new team or driver, practice results, all sorts of statistics, pictures during a race, meet-ups at a track, weekend weather at the track, something the drivers said about the sport, AMAs with members of the sport, something that happened at a local track.

On Topic: Something about NASCAR that is not directly about NASCAR but still definitively connected. Things like video games, diecasts, other merchandise, a major event in a driver/owner/crew chief/announcer's personal life like marriage or a kid or an accident or a lawsuit.

Acceptable Off-Topic: Something that isn't about NASCAR, but is related and of interest. A cross-post to an ARCA or IMSA or IndyCar or F1 race thread, a technology or rule change in another motorsport, a merger or bankrupcy in a company that sponsors a NASCAR team, a notable incident in a non-NASCAR race (if a NASCAR driver/team is involved, this straddles the line with On Topic), something important but non-Motorsports-related with a NASCAR manufacturer, something important with a channel that broadcasts NASCAR.

Totally Off Topic: Something that isn't about NASCAR, and has little to no relevancy to NASCAR. Literally everything in the world that doesn't have a connection to the sport. Football/soccer/baseball/hockey/wrestling? If it didn't directly affect a race or a driver, it doesn't belong here. Current events? Ditto, no matter how tragic. Politics? Belongs even less.