I'm with the 70w in.a.pinch.but.go.for.more club. More voltage is nice (but dangerous to modern boards!), More amps is really what you want to ensure you have though.
Before the ZW, there was the mighty Z. They are still around for under $100, sometimes $50-60. All that power to one throttle Mmm Mmm 
...or share amps with the other 3 throttles and more track, turnouts &/or accessories.
I find AF & Marx to be a little lighter than rated on heavy duty cycles. AF seems most heat sensitive having more heat v-drop, Marx just get very very hot.
The LW has the most power for single throttle Lionel units.(125w?)(@20v I think) VW and KW tie (2 throttle 180w)
Split of power isn't a 50/50 thing for 2+throttles. E.g. kw throttle A might use 120w today leaving 60w for throttle B..... it is based on need and availability sothrottle B might only use 25w today.... or it might use 90w and 90+120=210w more > than 180w so trips the breaker.
A few transformers DID split the power rating; there are actually two transformers in them.... mostly avoid them (tw or sw?)
Rheostats get very very hot 👶🍼... but also have a vintage feel that can't be beat. They allow most any constant power supply to be used..say... battery or.battery charger, ham radio/test bench supply, industrial transformer(&fuses/breaker), etc...remote mount the power if ya want; añd a tabletop rheostat footprint is small, takes up less room than the big rheo /breaker/transformer combos we usually use.)
Another vintage name is Jefferson Transformers. I think their Midget is 75w/12v, but it does well with engines that normally like 15v+
