Aye!!!!!!!!!!!! Lots of stuff.
Attached is my current layout and how it's currently wired up. I'm using FasTrack.
What specific items would I need to be able to use this accessory with the MTH DCS Remote? If I can't, then what specific Lionel item(s) do I need to use it with the Cab-2 LEGACY remote?
#1 you can control TMCC engines now if you have the 50-1032 MTH TIU to Base cable connecting. The problem is on the Lionel base side of this, they do not allow Legacy flavor of TMCC commands directly into the serial port via that method. Again, Lionel made the rules, so they want to sell you the LCS system and cable with an LCS serial 2. Such that the 50-1032 cable plugs into the SER2 LC box, that then plugs into the legacy base. And per that little note earlier, if you are going to use the screw terminal serial data out of the SER2 module (example to your AMC/ARC log loader, then you need a second SER2 module and DPI cable in the chain to perform the serial port to the TIU connection. Again, just to be clear today, if you have the 50-1032 cable between your base and the TIU, then you technically can control TMCC equipment with commands sent from a MTH DCS remote- but there are some limitations and so forth.
My advice, drop the idea of a one remote utopia. Lionel engines are best run with a Lionel remote, MTH engines best run with an MTH remote, and LCS items best run from LCS, but that is just my opinion and experience.
#2 "specific Lionel item(s) do I need to use it with the Cab-2 LEGACY remote?" Again, right now, nothing more than that serial cable plugged into the serial port.
Lionel cable (6-14191) which has a DB9 connector on one end and 2 wires that connect to the TPC on the other. (Or in your case, the AMC/ARC log loader serial input) Again, just follow the AMC/ARC Log loader manual https://www.lionelsupport.com/...ents/72-4115-250.pdf
The only difference is in this picture you have a Legacy base VS a CAB-1 base. Both have a serial port, both work the same way in this regard.
Also, see this topic about connecting all this up. https://ogrforum.com/...ase---tpc---plus-dcs