I don’t know much about conventional control wiring, but for the DCS Explorer or other command control you need to not just get power all over the layout but the data signal too. If you have three DCS Explorer units, each one will only send data to the train on the portion of track it’s on.
You’d probably be best off wiring all of your track to the one DCS Explorer. If you use multiple units, it would cause a lot of headaches.