Is there any major difference between gcc c executable project and gcc c asf board project?
The "GCC C Executable" project is bare bones (metal) project that is minimal to bring the device to a main function.
The "GCC C ASF" project incorporates software libraries (and source) providing a large collection of embedded software that can be used for the device. It is supposed to make it easier to get you going faster with developing your program. The ASF can at times be complicated (difficult to understand) because it was developed to be used with AVR and SAM devices. The levels of abstraction can get carried away and difficult to follow.
© 2020 Microchip Technology Inc.