For years now, I've been using a Garmin Nuvi LM2455, which is actually a car based GPS unit. I "waterproofed" it (actually water resistant) using information I found on a Youtube video. It's been in countless rainstorms over the past several years and it keeps on going.
The Nuvi has a feature called Trip Planner, which allows you to import .gpx files via a USB cable. I've downloaded .gpx files from online sources and loaded them onto the Nuvi, and the Nuvi would follow them with turn by turn directions. I've also created custom routes on both the old Tyre to Travel and its replacement, MyRoute, and uploaded them to the Nuvi with no problems. I did have trouble with the MABDR .gpx files; they were too big for the Nuvi, and when I tried to view them on Tyre to Travel, they looked like a plate of spaghetti and all the waypoints were out of order. I had to recreate those routes from scratch using the Butler map as a guide, to be compatible with the Nuvi. I've used the Nuvi and custom created maps to ride all over the country. It mounts to my accessory rail with a RAM cradle and a homemade ball mount.
I don't know if the non-car GPS units use the same feature called Trip Planner; they may, and it just might be called something else
The Nuvi 2455 is getting harder to find, but they're still out there. They've been superseded by newer models, but they're still cheaper than the motorcycle specific units like the Zumo. The Zumos, being motorcycle specific, are better in general. The screens are brighter in sunlight, and I believe they have some vibration resistant qualities. Still, I stick with the car based ones, because they work for me.
I've tried the cell phone based GPS (a Droid Turbo running OsmAnd) and I still prefer the Nuvi.