Just like for the CAB2, you need set the control type - as that is what then dictates what icons are shown. What you are seeing are the default TMCC icons.
Couple of bigger things though we need to get straight. The Legacy base is the "brains" of the system and stores the database of all engines, all accessories, all trains, and so forth in this database. Again, that is stored in the base. The Cab2 remote is dumb without the base. It's just buttons and icons I can display but again, what it does is connects to the database in the Legacy base. So when you set and ID (example from my layout is my cranes I set to ID3) in he CAB2 you hit info, then scroll through the setting tabs for that ID, and key here is, those are stored in the base so that no matter what remote connects to that base, that ID then displays those chosen icons (example crane car, TMCC, Railsounds 5).
So, in my iPad, running the LCS app, I access the "Roster"
Once you see the route screen, then you see the ID slots you have made in the database. There you can edit one, and then choose the correct control types (example again, crane car, TMCC, Railsounds 5) or if you have the Legacy version of the crane boom sounds car, then choose Legacy for Railsounds type.
Now in fairness, I'm running a really old iPad so my LCS app is an older version and the screens and icons might vary between versions? No to mention, I do not know the interface for the phone sized screen so where and how you access certain things, I may not be able to replicate.
Again, I just verified with the app, it's slightly different than the remote in that if you are not connected to the base, then you can edit things and that's in the app, and then when you connect to the base, you may get dialog windows as the app and the base database sync up. Again, just a minor difference, the CAB2 remote basically does nothing unless talking to a base, where the app being on a smart device, kinda has it's own database, but has to sync up with the base database so that the changes match.