About 8 miles, mainly flowing pinewood singletrack interspersed with fire roads. No great elevation changes but a few short and sometimes reasonably sharp hills, means it isn't physically as easy as the terrain might suggest off a map. Drains really well, even in torrential rain it would be rideable although the sandy soil does eat brake pads!
I'd say nothing too technical, maybe a couple of drops / roll ins off banks into sunken fireroads, etc. I didn't do gatcombe or 24:12 so no idea what to compare to. If there's one thing that could be an issue, it'll be that if it's wet after all this dry weather some of the roots are going to end up highly polished and they can bite if you don't pay attention.
Overall, it's a brilliant event - I'd say do it. Really chilled vibe, nice camping area close to the event centre, beer and band tent for later on, disco under the bridge to nowhere, tunnel of lights, and the chance to laugh at me attempting my first solo.