As far as which bike is suitable...that's up to the rider. Sections that are tough for bigger bikes are hard because they are difficult to ride slowly on these bikes. They don't 'tractor' slowly up hills like many 250s, they must storm through sections to carry enough momentum to make it. All bikes would make all sections with a committed rider.
It's easy to ride with others that are not in hurry to get somewhere, it's harder when someone has too much 'schedule'. I tend not to overplan or schedule, and let each day fold itself out as it may. I ride fast, but I'm never in a hurry. I'm on vacation when I ride, so no stress is allowed.
"got no problem with keeping truly roadless areas as wild....
On the other hand, if it has been logged or mined and roads already exist,,
...then that land should be open for public use" (peterman)