The difference between Mode 1 and Mode 2 is the layout of the throttle, elevator, rudder, aileron inputs (the two sticks).
Mode 2 is most common (thorttle and rudder on left stick, aileron and elevator on right stick).
Mode 1 has the throttle and elevator swapped.
Those transmitters you have linked are all the same, the only difference is that some are Mode1 and some Mode 2. and 2 of them come with receivers.
Edit: What will you be using the DX6i for? Just multirotors? Or planes / heli's too?
What is the difference between a transmitter and a receiver?
They're not built in, it just comes with one. The only reason you'd want to buy just a transmitter without a receiver is if you already have one or your flight system has an inbuilt receiver.
The 200 QX will also support many BNF-compatible transmitters. The BNF standard means a single controller can be used for many aircraft in your collection. A DSM2 or DSMX transmitter with at least 4 channels is required for aircraft operation.