If you want to go into engineering/computer science you need A level Maths and Physics for uni. So triple science GCSE is a must. Any further maths options would be ideal too but don't feel like you have to do this. Though getting an 8 or 9 in GCSE maths is crucial for a level physics. For your two other options:
- Computer science GCSE is quite a short course, therefore, it gives you lots of time to revise, plus it's not that academically challenging
- For your second subject I would suggest picking a subject you know you can do well in as that will be crucial for when you apply to university(esp the top unis).