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You didn't say what kind of camera and lenses you will be using the tripod for. It has everything to do with the weight you're going to put on a tripod. It also affects the kind of head you'll need.

If you're using a DSLR with a medium zoom lens, you'll need a tripod and head that can handle up to 10-12 lbs. You'll choose between a ball head or a pan tilt head. A ball head gives you very quick adjustment, while a pan tilt head gives you better fine adjustment.

Both aluminum or carbon fiber are good materials. The CF is more expensive. It is slightly lighter. Unless you have plenty of $$$$, an aluminum one is just as good. Stay away from the low end plastic ones with a plastic head built in.  Those are, more or less, toys.

The flip level lock let you adjust the height faster than the twice lock. But you'll need to tighter the screws in the flip lever clips frequently because they tend to get loose with use. The twist type is slower, but you don't have to worry about tightening it.

If you have a DSLR that can take video and you want to use the tripod for video, you'll need to invest in a video head. That is a totally different ball game.