One more thing Iwant to add. You mentioned that someone told you that a 12x6 prop is too much for a 3s LiPo.........That's a misleading statement. When choosing a prop, lots of things need to be taken into consideration, but the most important thing is the motor. Is the motor suitable to turn the prop you want to use? How much current will it take to turn that prop? How much thrust do you need? How much speed do you need?
There are plenty of motors out there that will turn a 12x6 prop with a 3s LiPo, it just depends on battery capacity, discharge rate, what voltage range can the motor operate on, etc.
As a general rule of thumb, the lower the kv rating, the lower RPM the motor is designed to run at, but at a higher torque level. The opposite is true also, the higher kv rating, the higher RPM range the motor will operate in, but less torque. So, knowing this, a lower kv motor will turn a large prop at lower rpm's, and a high kv motor will turn a smaller prop, but at a higher rpm range.
You also need to invest in a watt meter, that way you can try different props, and actually see the motor draw so you don't overdo it, or vice versa.
You need to try to figure out what the required thrust will be to fly that model, and go from there. Keep in mind though, as you add power, you will also be adding weight-bigger motor/ESC, higher capacity batteries, etc. So it almost becomes a 2 edged sword, so to speak. Once you know the general thrust requirements, then you can decide which prop, and subequently, which motor/ESC/batteries to turn it.Hopefully that helps you more than confuses you
