As PGentieu stated, the transformer you picked will not have enough power except for maybe one engine. I quickly checked Amazon and they have a few step down transformers from 110 to 15-18 VAC but all produce too little wattage. The one I found that had good output power was over $100.
Also, the PowerMaster requires a special plug and was made to work with a PowerHouse 135 or 180 to run conventional engines with the handheld. You can get this plug, but just more hassle.
My recommendation is to look for PH135. You can find this at a low price now and then.
ADDED: You posted while I was typing. You have everything you need to run TMCC and conventional. Are there instructions in the box.