SAVE folder is almost mandatory to delete. Only if you have saved your points and the like, but that can be backed up separately.
If navigation software and no other is in internal memory, you can format it (FAT32), just in case. And you should be able to adjust navigation path from device's settings, so you could run iGO from (good) SD card. This is the best solution to eliminate problems with the device itself.
EU+AU, alte save, they are put in by users. gpsnvm.bin is created by software, and will be created again.
Earlier, most users were crowding as much content as possible, also every dll, also every license file...most still do.
In the meantime, we learned a little knowledge
There is a lot of discussion on the Forum about this, mostly this is a short one.