Filling in the route field of a flight plan is to inform ATC of your intended route - so you can use published intersection names.
Most flight plans are now automatically extracted. In the '70s I wrote software for an Automated Flight Data Processing System for ATC to automatically extract the route from the field 15 description. Such software is now common, but the specifics do vary from place to place. As noted before, VFR plans don't get sent to the IFPS at Brussels.
What you can use in the route field is defined by ICAO. Ignoring route names (airways) which you won't use, the points can be VORs, NDBs, published waypoints or intersection names, lat long, or bearing distances.
I don't think that local names - such as towns - will be extractable, and might provoke errors and be rejected by the data processing. Depending on the ground system, a town name may be acceptable because it is processed by the Mark-1 eyeball.
If you use bearing/distance references you will get around these problems.