Running conventionally, any transformer will have essentially the same behavior where this same Locomotive runs at less than full speed but your passenger cars lights are not at full brightness. Legacy, LionChief, LC+, etc. overcome this problem by supplying a constant 18V to the track and controlling the engine speed remotely via electronics in the Loco.
But, yes, the MTH Z 1000 should be sufficient for your current set-up, however there may be better alternatives for you. One thing to consider is that MTH is going out of business, so... warranty? parts?? Other things to consider would be in the future, how may trains might you be running at the same time and do you want to have one or more separate outputs for accessories. If you only want your back-up transformer to run one train at a time and want a dedicated accessory output The Lionel CW 80 might be a good choice. In fact there is one listed for sale now here on the forum ( and if you're wondering, I don't know or have any affiliation with the seller). https://ogrforum.ogaugerr.com/topic/lionel-cw80
Good Luck!
