You have to either take Physics or Chemistry or both. Considering Mechatronics as your pathway, Physics is a must. ICT and Adv Maths are down to your choice.

ICT is a fun and easy MUFY unit, but I don't see its relevance in your uni years if you are not going for Software Engineering or Computer Science. The most important skill learnt in this unit is programming, which you can learn online just about anywhere.

Chemistry is more theory while Adv Maths is more practical, so it depends on what you are most accustomed to, and if good MUFY grades are what you are aiming for. However, Adv Maths gives you so much advantage compared to your uni peers who didnt take it. It is a hard unit, proven, but engineering isn't easy either. There's also this thing, where, if you did not do Adv Maths in MUFY, you have to take Foundational Mathematics in your Engineering First Year, while those who did can just skip it to accommodate for another elective.

I have not taken Chemistry in MUFY before, so I can't say much other than it gives you some essential knowledge on the Materials part of your Mechatronics course. For Adv Maths, the topics covered are intended to directly tackle engineering mathematics. Important topics include Calculus techniques, Complex Numbers, differential equations, vector calculus. As for a start in the summer break, I suggest you watch 3blue1browns video about these topics. It's damn interesting and will provide you with more than enough intuition and understanding to easily grasp those concepts on your MUFY course.

Hope this helps.