Just three remark!
1) On some device like Nuvi 2x5 when you delete text file you also lost abilities of keyboard on that language.
2) You can clean track archive, on my nuvi there is subdirectory \Garmin\GPX\Archive. But new data will again record by passing time (limit in hardware - 20 archived files is about 20Mb) and if you do not have reservation for that volume, device will not have sufficient memory for recording service files sometomes that is not good.
3) Deleting help files give much more size on disk then 2Mb. Due specification file system many little files as help required more space on disk in about four times.