Races would be cx, participation events would be gravel.
There's a pretty active cross season in NC it appears. But there's also stuff like the Umstead gravel grinder I'd like to try. That's 100 miles of gravel and some pretty challenging total elevation.
So, fatigue would matter on the gravel stuff given I'd be out there for 6-8 hours.
I'd want some out of roadie season training rides to be in the 3-4 hour range on the gravel in Umstead.