1.) yes, the files were generated from a power delay profile. The procedures can be found in +channel_gain_wrappers. The type of channel as well as other information are found in the object pregenerated_ff, which is stored in the channel_trace file.
2.) Yes, it does. The idea is to store trace files in order to repeat multiple simulations with exactly the same setting.
3.) The RandStreamSeed will not affect the files directly. It basically changes the position of the channel slice, which is taken out from the channel trace in order to carry out simulations.