IMO a Nomad has two drawbacks over a dedicated mountain bike:
- it is designed as an expedition frame, so is heavy. More difficult to lift over gates, stiles, fences.
- no suspension. Dan's Thudbuster post should help. I have a sprung Brooks saddle on the bike I used most for survey work (a lot of riding on paths and tracks). Using the fattest possible tyres inflated to moderately low pressures also helps.
And one big advantage over derailleur-equipped mountain bikes:
- Rohloff hub gearing is much easier to keep clean, even more so with a Chainglider.
Mudguards are a nuisance off-road as they clog with mud/wet sand and trap twigs. But I prefer to have them in moist Atlantic coast conditions. As Dan says, leave plenty of clearance between tyre and mudguard, there will be more room for this on a Nomad frame as compared to the frames I have.
For survey work with a mix of riding on tarmac and paths/tracks I preferred to have a fairly smooth tyre, the fattest I could find that will fit the frame. Fat so it doesn't sink too much into soft surfaces, smooth so it rolls well on the tarmac stretches and so that it doesn't spray lots of dirt sideways like a proper off-road tyre. This is a compromise, and I sometimes had to push or carry the bike over some very muddy stretches that would probably have been rideable with dedicated mud tyres.