I hope someone will correct me here if wrong, but this is what I've done. I'm using my dad's and grandfather's old postwar transformers. That gave me 6 to start. I picked up another TW and 1033 from that era and a modern Williams as part of a set. Six transformers go to track (5 loops, one yard), three to accessories and lights. They're all in phase.
I added a Lionel Powermaster to each power block going to track. I bought them all used for $20-$25 each, so my all-in cost was less than a new Z4000 or ZW-L. The PMs provides the quick acting circuit breaker others have suggested PLUS the ability to run conventional with a CAB-1 handheld (they also convert the old PW transformers' output to a chopped sine wave that TMCC engines want, but I don't think that's your goal).
At others' suggestions, I added a TVS between the terminals on each transformer going to track.
