Use one and only one command base for the layout. You can use multiple Cab-1's but not more than one command base. The TMCC signal is carried on the outside (running) rails which are also the common side of the electrical circuit (as opposed to the center rail which is the hot side). Just make sure the outside rails are joined together electrically.
The OGR video on TMCC is very helpful, straightforward, and a bargain considering the time and aggravation it will save: https://ogaugerr.com/web-store/lionel-tmcc-system/
For DCS, I would recommend Barry Broskowitz's DCS Companion: https://mthtrains.com/DCS_Companion.