3. Pick competitions that match your category and strength.
This makes sense, and I guess your reason for success in both competitions that you have been in is based on this fact.
The general advice is that you should avoid trading competitions because there is an uncertainty that you will be able to handle the pressure that comes with, as many people can't. But if you are certain that you can handle the pressure and you have the strategy and psychology to support it, then you can actually make some money from trading competitions.