Hi Dave,
Both Marklin and Trix are HO scale. As far as I am aware, they are made in the same factory. Trix and Marklin locomotives (and rolling stock) are essentially the same, aside from the fact that Marklin is a 3 rail system (they have a central electrical contact on special tracks). Marklin locomotives (and rolling stock) are incompatible with standard 2 rail pick-up systems. In other words, if you have a standard 2 rail setup you can run Trix locomotives just like any other 2 rail brand (Hornby, Bachmann, Athearn, Atlas etc). You can use standard tracks to run Trix models (Peco, atlas, hornby etc). If you run Marklin locomotives, you need Marklin specific, 3 rail track. There are pros and cons for both systems - I won't go into it here in order to preserve the peace - suffice to say I own Trix....
Rob

Trix is an sister company to Märklin and they produce same locomotives and wagons.
The only difference are wheels and pick up shoes to power feed the loco.
Two rail use isolate wheels while Märklin use non-isolate wheels.
You can buy Märklin wagons and change out to DC wheels for free.
You can buy Trix wagons and change out the wheels for the Märklin tracks.

no need to change the wheels unless you use occupancy detection blocks, never had the need so can't say for sure. My trains are digitally controlled but I will never connect a computer to my layout to run it for me 😊

This is why I am on the Märklin 3 rails system and don't hink in buy some other stuff. I know I am limit myself this way, but what I have runs without problems. I just don't like the turnouts in the Märkllin system.