[GpsFrontier]

Living in South East Asia the temp can be pretty high, summer 30C - 39C. This is why I am thinking about using the deep pond floating raft technique where possible and an ebb and flow system of Dutch buckets (if I can find them here) for plants that can not be planted in deep pond floating raft systems. Mainly peppers and tomato.

Not sure what that temp is in Fahrenheit, but I am guessing it is about 100+ degrees Fahrenheit. In Asia I would probably be more concerned with the humidity, more than with what the heat like I deal with here. I am not sure Where/why you plan to buy dutch buckets. They work just fine but I can build them much cheaper in my area using 2-3-5 gallon buckets (less than $3 each for a 5 gallon bucket). They just need to fit inside each other the same way, then modified appropriately.

1 A simple small tank with airstones (like in the forum here)

Not sure the question here. Yes air stones provide air/oxygen to the roots. Especially in a water culture system, but is the question does this work? Or how much air is needed? It works, but how much is needed depends greatly on the size of the system. As well as other factors like temperature and if there is any addition of dissolved Oxygen like H2O2 (or even 03 from ozone treatment) into the nutreint solution.

2 A longer tank with on one end a horizontal pipe that drips solution in the thank and on the other side a hole where it flows back into the tank. This creates a small water flow.

This creates water flow yes, but does not introduce much needed oxygen/air into the solution by itself. I'm not sure if you are referring to a typical NFT system, or a overflow system for a water culture system. I assume it's the latter.

3 A large swimmingpool size bath full of rafts.

Not really sure how deep the swimming pools are for you, but it shouldn't need to be more than 1 to 2 feet deep, the root systems wont need more than that.

What system is better? Or is it a matter of trial and error?

Nether is best as far as I can tell. They both have there advantages and it simply depends on what you plan to grow in it that makes it a good choice or not. Tall plants that need support wont be the best choice in a water culture (floating raft). The design dimensions make a big difference also, as to how much weight it can support without failing. But it comes down to a few factors on if this is this is the best choice for the job, Amount of nutrient solution required for the operation, and weather the structure can support the intended plants. If it cant support the plants, you can always build a support structure. But weather it is cost effective compared to using a different system is the issue that I think you are concerned with.

How do they aerate the water in the large pool size ponds?

I don't know how much water you are talking about (gallons), but With a number of ways. Oxygen in the water, and water circulation are the keys for suspending roots in a nutrient solution. Otherwise they will suffocate. Large amount of air stones in a large setup may not be practical. In that case water flow is even more important. Large operations may even use Ozone treatment, this adds even more dissolved oxygen to the water, and inhibits root disease. Cost can be an issue though. Large air pumps with good water circulation may be a better option for most smaller operations.