Before this thread starts to make you dizzy.
DCS also has a "preferred" wiring style. Star wiring.
The layout should be broken up into separate isolated blocks with one pair of hot and common feeders to each block from the TIU, which is the DCS "command base". I believe the blocks should be limited in length and/or track joints.
(As dizzy as it might make you. You might be better off selecting a previous thread that is easiest for you to understand.)
Having said all that. Roy's and PC's recommendation of the Legacy powermaster isn't a bad way to get your feet wet with MTH products without modifying your layout.
The Legacy powermaster allows conventional operation of MTH locomotives via the legacy handheld. You'll have access some passenger and freight announcements, as well as the whistle, bell and electrocoupler.
MTH locomotives have PS2/3 a battery or BCR integrated into the electronics so there are no sound dropouts when changing directions conventionally. Also in my experience, MTH locomotives run very smooth under conventional control, and once under way its hard to tell they're not under DCS .
*There are other potential issues with adding a DCS system that may need to be addressed. I.E. possible signal interference from Legacy locos and fastrack LEDs, that don't effect MTH products in conventional operation
