When traveling, I have the 12" InCase neoprene sleeve for my rMB, and I use a RadTech ScreenSavrz to protect the screen from the keyboard. (I also use the ScreenSavrz at home, every time the machine is closed.) I take along a tiny little Nonda adapter plus an equally tiny little Sandisk 64 GB Dual Drive USB-C/USB 3.0 Flash Drive (available at the Apple store), as well as a Satechi adapter which has two USB-3.0 ports plus charging passthrough. Oh, and also a very small Satechi dual USB-C/USB 3.0 SD/mini SD card reader. That, plus of course the Apple charger and charging cable pretty much takes care of anything I might want to do on the road. I also take along the very small Samsung T3 SSD external drive which has supplementary files and folders on it in case I need to retrieve one of them, plus space for including new material if I might be adding it while on the trip.
The tiny little Nonda and the Sandisk Dual Drive Flash Drive fit very nicely into a small plastic box which once held a lens filter. That way I don't lose either of them and they're easy to find in the bag if I am in a hurry. The other two devices fit into a fairly small pouch.
Depending upon the travel situation and the length of the trip, I will either stash my electronic gear into an Osprey Pixelport backpack (usually I take along my iPad, too, but not always) or I will pack the rMB and its accessories into my rollaround carryon bag if it is just a short weekend trip and I don't have a lot of other stuff and clothes to pack, too.
If just going out-and-about around town, it again depends on the situation. If I'm going to a friend's house and taking my rMB I usually will also take along the small adapter and flash drive just in case we want to share image or other files, as so far I'm the only one of my friends who has an rMB or any device with USB-C. Since I still have devices with USB 3.0 here at home, I also use the dual drive or the Nonda with those, too, as needed. I also have a cable with a Micro-B plug on one end and the USB-C on the other end so that I can plug in my external drives which have Micro-B connections and that way can use them with my rMB as well as my other devices without needing the adapter. Just swap the cable to suit the computer I'm backing up or transferring files into or out of and I'm done.