Please refer to the following Application Note:
This describes in detail about the difference in implementation of an application in FX2LP and FX3. Please read the above document from Page 7 to know about the differences in software. FX3 examples provided along with SDK makes use of RTOS. We do not have an example for USBBulkSourceSinkLED without RTOS. We recommend that you develop the applications by making use of RTOS as it is not difficult and will not take too much of time. Please read from page 9 of the above application note to understand FX3 firmware framework better.
Also please refer to the FX3 Programmers manual which can be found at
C:\Program Files (x86)\Cypress\EZ-USB FX3 SDK\1.3\doc\firmware
Please refer to Page 58 of FX3 Programmers manual to understand the firmware code flow. Comparing this with any example project provided with FX3 SDK can help you understand the use of RTOS better.
Also, Can you please let us know what exactly is the application?