Re. suitable bikes, there was a huge cross section this year, 29ers, crossers, proper race bikes, the works. Do bear in mind that the majority of the route is road, there is not huge amounts of off road at all so don’t get too hung up on it.
I think the perfect bike for this would be a road bike with 28 or 30mm road orientated tyres, think a Paris-Roubaix bike. However, I rode my standard alu roadie with 25mm slicks and it was fine, I took it carefully on the unpaved sections as I didn’t want puntures and got knocked about a bit but generally it was no problem at all.