Newbie q's re: leashing, etc

Destructiveness depends on the breed and age and, even among particular breeds, varies from individual to individual. I have never raised a BMD, so I can't say for certain how they do when left alone, but I have raised two GSD pups (fortunately, not at the same time) and can say that that was certainly a challenge. While Max was relatively low-key and easy, Dash was, as I like to call him, the black-and-tan tornado. He was about 1 year old when I came home to find an entire sectional sofa bed trashed. He literally ate me out of house and home when he pulled and chewed several pieces of vinyl siding (of a discontinued color). Although he turned into one great dog, I truly learned the importance of crating, especially for ANY dog under 2 years of age (and some for longer). There are collapsible fabric crates (e.g., Noz2noz) that can be used for even large dogs and are perfect for an RV (they can be stored easily when you don't need them). The hard-sided crates are good if you have space for them and are worried about the dog eating through the softer ones. In either case, it is important to get the pup accustomed to viewing the crate as a den or safe haven (never use it for punishment) before taking it on trips. Good luck.