New to command control Question

If you have seven independent loops you want to run remote control conventional locomotives on, you need seven variable channels.  You'd need four TIU's to do that as each has two variable channels.  You'll also need probably four bricks, one to power each TIU.

If you limit the PW conventional locomotives to a maximum of four loops, you can probably do the whole layout with two TIU's and the four bricks.

Lionel PowerHouse 180 transformers are excellent power for the TIU, I use them, and our club uses them.

Piece of cake to add Legacy, just add the Legacy #990 Command System and run a wire to the outside rails and you're running Legacy.