To answer your questions:-
1/ Yes, analogue bandwidth of 200MHz is available on all ranges. The single shot sampling rate is reduced from 200M samples/sec for one channel to 100M samples/sec for each channel when two chanels are used.
2/ Input impedance is 1M ohm in parallel with 20pF. A 10:1 probe has a series resistor of 9M in parallel with a variable trimmer of about 4pF. That gives you a 10:1 resistive divider and an approx 10:1 (but variable) capacitative divider. The trimmer is used to adjust the response to square wave edges and high frequency measurements.
Impedance matching is important at high frequencies. If you are measuring RF coming from a 50ohm system, the 50 co-ax lead must be terminated at the scope end in a 50ohm load. Easiest way is to use a 50ohm "T" piece (BNC) to connect the lead and the load to the scope input. The 1M input impedance of the scope will have no effect on the measurement (1M >> 50ohm).
3/ Trigger modes of the 3206 are:-
Free Run, Auto, Repeat, Single and Save To Disk On Trigger
Here is a link to the 3206 specification:-