This would belong in the Ask a Question, Get an Answer, for future reference, but:
1. Not sure what a pump launcher is, but string launchers are generally the best choice.
2. Synchromes are far superior. However, in the Limited format, they are banned.
3. There is no best type. It depends on which you like the best and which parts you have.
4. The only "technique" in beyblade is customizing and launching, and neither require much skill, though some launches take some practice. Speed is a part of Attack types, generally, and isn't really comparable to technique.
There are some metal saga beyblades that are still competitive, but Synchromes have become a prominent part of Standard format. However, in Limited, the legal metal saga beyblades are more commonly used than Zero-G beyblades.
“In the course of twenty crowded years, one parts with many illusions. I did not wish to lose the early ones. Some memories are realities, and are better than anything that can ever happen again.” -Jim Burden (My Ántonia)
