I use a Salsa Warbird gravel bike with 38 mm tires, it has drop bars like a cx bike. I find this the best bike for these railtrails/dirt roads. I also have a Salsa Vaya which I have used in the past for these types of rides. I use a 29er for singletrack/mtb trails but I like the drop bar bikes much more for rail trails with the correct tires and setup. There is a very good selection of these bikes now.