I haven't read the whole thread, but to clarify a couple things I did read:
mAh is the battery capacity. Think of it like your fuel tank in your car. The bigger it is, the farther your car can go on a tank of gas. But it needs to fit in the car. Typically, the more mAh a battery has, the bigger the battery will be.
Voltage (1s, 2s, 3s, etc) is like the fuel octane. The higher it is, the faster your car will go. 'S' represents the number of LiPo cells the battery has. A single normal LiPo cell has a nominal voltage of 3.7V. When charged it will have 4.2V. So a 2S battery has 2 LiPo cells in it and has a nominal voltage of 7.4V (2 x 3.7V), and a charged voltage of 8.4V (2 x 4.2V). A 3S will have 3 cells and have a nominal voltage of 11.1V (3 x 3.7) and a charged voltage of 16.8V (3 x 4.2V).
When first getting into RC, it will be pretty expensive no matter what you buy because you will also need a charger. And buying a cheap charger is not only a bit risky, but you're just throwing your money away when later on you realize you need a better charger. You can buy LiPo chargers for less than $100, but there isn't a single one out there I would recommend because they are all the same cheap crap. The only entry level charger I would recommend is the Hota D6 Pro, which runs around $120 or so.
But even before that, as recommended, you need to educate yourself on LiPo charging, care, and safety. LiPo's are completely safe, but if not cared for and charged properly, they can be very, very dangerous. You could stick with brushed motor RC's and just stick to NiMh batteries, but NiMh batteries aren't that good compared to LiPo batteries as far as run time and performance are concerned.
The two trucks you listed: one has a brushed motor /ESC (electronic speed control) in it, and will do fine on NiMh battery packs. The Raptor is brushless, and will have to be ran on a LiPo battery, because brushless motors will draw a lot more amperage from the battery, and a NiMh battery cannot deliver that amount of amperage.
You did the right thing by joining here and asking questions before jumping into this great hobby. Keep asking questions. The more you learn before you buy, the better your entry into the RC hobby will be