For a better idea of the power split on the tw, go to Olsens Trains find the library (upper left on one of the pages) look into transformers... then I think the very top selection is also labeled transformers (vs the specific IDs below that) In there is a chart of amp expectations for all the old units (use volts and amps for the math to get watts, but amps are a bit more useful) I think it's a 3.5a acc. and 4.5a track limit (thermal) about equal to a 1032 or 1033. (of note, there is also an ultra rare twin transformer KW.... or I was sent the only test prototype with my LSA-Mercury set)
Another thread today had mentioned the new Legacy PM may also need the tui,command base or whatever they call the the command control module (I hate confusing buzzword titles) Older ones and tmcc, just the PM is needed for conventional running of locos.
Im not sure if switch control needs a command module to send a command signal, but I'd expect so.
That is a big price jump for the whole Legacy shebang plus L-PM to run conventional only/with sw control. If you can live with conventional running by remote and keep switches manual, that's the low buck option. (those deep into command tend to push you towards more than you may want or need IMO)
The tvs isn't needed for PW stuff. It is for modern electronics, mostly engines or acc./cars with boards. One between TW and PM, maybe another on the PM outputs would be what to do there, with no command things to operate on track or acc. There may already be one inside too...? More doesn't hurt though. On a command engine is the best place, on track here & there next best. Ie. as close to boards as possible.
I also think I recall the PM already has an excellent circuit breaker to supplement the TW thermal breaker. I suspect the input side of the PM to be pretty stable though.
The bricks are cheap and powerful, but kinda useless without a working remote. A thottle transformer can always stand alone in a few secondz when a remote's battery dies one evening 
