You can do fine on a road bike, if it is set up for touring. This means wide (37mm or so) tires. These ride fine on pavement, crushed rock, and dirt roads - probably not so good for hiking trails, a situation where mountain bikes indeed rule.

I prefer clip pedals and low cut hiking shoes. This combination allows me to do 70 to 80 miles day after day with an occasional 100 mile ride, all with one shoe that I can hike in forever and still use on the bike. Clipless pedals are just too fiddly and adjustment prone in my opinion. I get the impression that some clipless rigs also tend to cause knee problems. I read comments on bike touring forums from other riders who feel the same way. The are many options for pedals and the best thing to do is start riding and see what works for you.

I started with a touring bike frame (basically a longer wheelbase compared to a road racer). It is quite elderly now and I find over the years I have replaced a lot of original components with mountain bike equivalents. Since I have about 40-50 pounds of gear with me, depending upon the water I am carrying, I paid significant money for 40 spoke rear wheel, 36 spoke front wheel with Phil Wood hubs, custom built at my local bike shop. About ten thousand miles and not even a hint of a problem. A lot of my gear and clothing comes right out of my climbing/backpacking closet. If I ever had to abandon the bike, I would just rearrange the load and hike on. If you are used to riding it, a bike is a very feasible way to bug out. If you are not used to riding one, after a week or so, you will be....