Hello there! I suppose you’re reading this post in hopes of understanding what ModReg is like while exchanging with NUS. I, too, was very daunted by the need to map everything properly while ensuring that I met the prerequisites from NUS. After submitting my initial list of modules to NUS, I only had 3 courses I was accepted into, meaning to say that I had to find another 2 more to satisfy the requirements of SUSEP. I have consolidated some useful links just in case you are met with a similar situation!
NUSMods https://nusmods.com/
NUSMods has all of the modules available at NUS. For each module, you will find a short description of the module (which can be used when you are doing the Transfer Credit form!), possible pre-requisites of the module, whether it is available for the semester you are in, comments about the module and the most important function of all – the “Timetable” function that allows you to check that you do not have clashing classes. If you are unsure if you have met the prerequisites, I suggest you write to the NUS staff (nghelp@nus.edu.sg)!
This is what my timetable looked like for the semester! 
Module Vacancy Report https://nus.edu.sg/coursereg/resources.html
This was quite an important resource when I was looking for 2 other modules to take. You will be able to see the number of slots left after each round of registration for non-graduating students. This allowed me to strategise and decide which modules to apply for during the next round of module selection.
Here is the final list of modules that I was enrolled into:
Hopefully, you’re able to get pre-allocated the modules that you wanted to take! If not, fret not, you can always appeal/check with the NUS staff whether you can bypass the requirements 🙂 If all else fails, be open-minded and look for other modules which might interest you!
All the very best for your upcoming exchange!
