Another method many longtime RVers use is to pad the space between items. Some people like to use their kitchen towels for this. Since you will be using them anyway, make them even more useful when traveling down the road by placing them between breakables in the cupboards. You can also use cut up pool noodles or pieces of poly foam pipe insulation to pad the open spaces between items in the cupboard. Whatever item you choose, they will all do the job of preventing glass and other breakable materials from clacking, bumping, or rubbing together.
Before you leave and head out on the open road in your RV, it is always good to check and make sure everything is secure. Make sure every cupboard has been closed and fully latched shut. If you are still worried about the possibility of a cabinet door coming open during your ride, you can secure doors further with baby latches or make shift latches made from rubber bands. You should be ok with just making sure the cabinet is fully closed.