Form 6 is a waste of time (ok too lazy to talk about the dis/advantages of this)

with 10As, you could try applying for scholarships to further your studies... To my understanding A-Levels/Matrics like OSSD, AusMat, SAMs/ADTP are all world recognised. But most would say that A-Levels give the widest platform to continue from to further your studies.

No doubt A-Levels is the best option, but it's also the hardest as it's all theoretical. Matrics like OSSD or AusMats tend to be slightly easier as they split their course to half assignment based and half final exams, so it focus on both theory and the application of theory.

The choice is up to you, you have to see whether are you a book person or assignment based person. Try going around Open Days or Edu fair to ask for more details about their courses