I also asked this question to my form tutor.
Double science is basically two of the three sciences, out of physics chemistry and biology. Now, if you do two sciences/ double award, then you only do two science GCSEs. This can be seen as easier and most likely your teachers and mentors will guide you to which two of the three sciences you should choose based on test scores, classes and which two you are best at.
If you are ambitious, triple award is all three sciences - physics chemistry and biology. These account for three separate GCSEs and more work generally but worth it in the long term. Triple award is better than double award and for more capable people like you probably.
If your ambitious, after sciences triple award GCSE, you can do a post year 11 GCSE on additional sciences, im not sure what it is but i've heard rumours and links to special science courses for advanced science courses.
Triple award, alot better, more worth it, if it is compulsory. Think about your optionals. If it is compulsory then take it. It may be slightly harder, but worth it, trust me.
hope this helps! :)