Data width is a basic parameter, it determines the data size read/stored by DMA (byte, halfword, word) through its ports (Memory, Peripheral).
Burst size, FIFO threshold are parameters used only in the dual-port DMA (used in 'F2/'F4/'F7, see AN4031) and they are used only if FIFO is used. You don't need to use FIFO, in most typical applications it has only marginal benefit at the cost of significantly increased complexity. If you use Direct mode (which means no FIFO), you don't need to be concerned about these parameters and they may take any value.
If you want to use FIFO, read the DMA chapter in RM, and AN4031, thoroughly - the answers are there.
JW
