Noob question regarding slide-in campers /trucks

Cab size is mostly irrelevant. I carried a camper on a 3500 reg cab for a couple years. The cab-over did stick out a bit far but it didn't look bad and it handled fine. I was able to fully open the hood with no problems.
The lighter your truck the better because truck campers are really heavy. For one that size don't dare go less than a dually. You might even look at a F450 or a Ram 4500 with a flatbed.
The only possible disadvantage to a reg. cab truck is getting the camper closer to the front axle and overloading it. This is unlikely unless you have a 4wd, diesel, with a huge aftermarket front bumper with a winch, etc.

Just be careful when you open the hood.... Your camper and the hood might become close friends.