You should be able to find that in the TRM of PSoC.
You can trigger multiple DMAs at the same time, by connecting them to the same trigger signal. But they won't actually run at the same time - their transfers will be in sequency. Look at the TRM for more detail.
But yes, doing so simplifies things since there is no need for a custom trigger component.
I asked a similar question here.
In my case, was enough to make a shift in the signal table and perform CyDmaChEnable with some delay.
In short: There is a priorization between the different DMA-channels running in parallel.
Since you do not specify much about the problem you have got it is difficult to give you advise.
But be sure: a single DAM channel running to transfer data will always be faster than multiple channels performing the same shared job