What data will be lost when exporting from "gramps database model 5.0.1" to "gedcom database model"?
Gramps 5 allows you to adjust the content of the GEDCOM to suit the intended use (identified by the software to receive the file), so the precise answer to your question will depend upon the option you choose. Some targets will involve more 'loss" than others. If you intend to use (plain vanilla) GEDCOM 5.5, then anything not specified in the standard (see http://phpgedview.sourceforge.net/ged551-5.pdf) will not be included.
For more detail about export options refer to:
- GEDCOM import Gramps 5.0.x User manual.
Also read the the "Lost information on a GEDCOM export from Gramps" section.