Assuming you mean NCN780 then the choice is yours. Apart from an optional detour along the machair on South Uist – or along a beach – you’ll be on road the whole time. Something like a Schwalbe Big Apple might make it slightly easier going but you shouldn’t be in a rush anyway 🙂
I see the walkers version of the HW has just been officially launched. From the bits I’ve seen/know I remain to be convinced that it would make a good ride. There are some off-road sections where a 3″ bike might well be the best option though.
Enjoy the ride. It seems to be very popular this year, perhaps based on last year’s NCN780 launch with Mark Beaumont. It looks like we’ve drives to/from Ullapool/Oban most weeks over the summer.