Your question about the amount of single track and fire road indicates that you need to better understand the nature of the event. If you can visualise 15 or so checkpoints scattered over a very wide area of North Wales (about the size of 11/2 OS 1:50,000 maps) you have about 48 hours to get to as many checkpoints as you can including sleeping, eating etc. To get them all involves route finding and optimising the amount of climbing down to about 23,000 feet and riding about 140 miles so it’s not easy.(I know i did just that) The question regarding singletrack etc is entirely dependant on your choice of route, if you wanted to do a lap of the Climaxx trail in Dyfi forest, you could but it wouldn’t get you any more checkpoints, if you want to ride 10 miles along tarmac lanes to avoid a climb up and over a big hill, you can. It’s a matter of deciding what you want out of the event. Think of it as the organiser giving you some hints as to where some good riding is, if you chose to go there.