Everyone's different and I've known at least one runner who wore training shoes for biggie 100-milers. In my case, when I started running trails in my area (NE Ohio, mud, slick clay, roots, rock, off camber, steep inclines constantly) I found that any road shoes I tried had too little structure and grip, not only in the midsole or outsole, but in the fit of upper itself. I needed a little structure and a good trail fit so that when my shoes/feet are being torqued in all directions, my feet stay secure in the upper. I also need some side and toe protection, and a rock plate is nice too.
I couldn't believe how much better trails were when I started to use actual trail shoes like the Peregrine and Speedcross. The question becomes how much do you need to keep secure and moving fast on the technical parts, where structure, protection and lugged outsole with grippy rubber will help tremendously, while not feeling like you're strapped into boots for the easier portions, especially on asphalt.
There are plenty of trail-oriented shoes that are made to be runnable on asphalt too, "road to trail" types. I suggested Salomon and Hoka because they offer several models that are right in this wheelhouse. Of the Hokas, I don't like the Clifton for ANY technical work because the outsole and structure of the upper aren't going to provide the traction and support you need IMO. Terrible in the slippery muck, ankle breakers on rocks and roots.
I would look at the Speedgoat 5 way before the Clifton. Of the Salomons, I would look at the Ultra Glide and Sense Ride 4 models. Enough structure, grip, traction and toe protection to help get you through the technical stuff, and actually built for it too, while cushioned and not too deeply lugged (outsole) to be bad on road.
YMMV. I'm doing a 50K on mixed asphalt/trail in November and will probably pick up some Ultra Glides for that one. Best of luck with the shoes and the race.