Power sources

More info is needed for proper reply.  Are you planning to use Command Control (remote)?  Lionel or MTH?

Two MTH Z4000s will be a good start for your needs.  The postwar ZWs would need an extra sound control box for whistle activation.

My power is mostly postwar ZW and Z.  For modern era, my control is through the MTH TIU and Lionel TMCC or Legacy.  I do have 3 MTH Z4000 transformers for conventional remote control.  Each of the Z4000s will power two track loops and lights/accessory 14V power.  Postwar ZWs and Zs are ideal for lighting and accessories because they're variable voltage.

Nowhere near that sophisticated.  I could probably get by with the original transformers but doubt they'd work over the length of the tracks, which I can anticipate at 80' give or take a bit

I am running a TOY train (Marx 027) and don't need a lot of bells and whistles, just stop, go, and speed control.

Transformers aren't affected by length of layout.  They are affected by the amperage drain which they are called upon to produce.  If your wiring is inadequate, no transformer will do the job.  Given the current draw of old locos, which I read you as saying you'll be running, I wouldn't use anything less than 14-gauge wire.

With any old transormers, I'd use an external breaker sized per the wattage rating of the transformer.