Train transformers are not regulated, so you would get power surges, even with a large one.
You can use Parma controllers with either positive or negative wiring. If you are going to use a large power supply the track wiring must be able to handle the extra power, in addition there should be a fuse or circuit breaker for each lane.
Here are the two ways of wiring a track. Negative polarity is the way all set type tracks are wired, the positive polarity method is the way most wood tracks and 1/24th commercial raceways are wired. Many electronic controllers come in positive polarity versions only.
To convert a negative polarity track to positive polarity all you have to do is switch the wires at the power supply and also switch the wires that connect to the track rails.