In my research, I found a TIU (especially a REV L) ends up being the best bang for the buck...even though they’re fabulously expensive right now. This TIU has apparently squashed previous issues with signal, and other ‘problems’ associated with earlier versions.
I’ve also read the explorer has issues running various PS 2 engines.
From reading the manual included in my new subway set, and the DCS companion book, many of their features are available running subways conventionally.
Tom