Amazon has a picture of the Ultimnate One on their website, and it is nothing more than an Ultimate without the Hub, or the former Touch which came out befor the Ultimate. They then added a Hub,tilt sensor and a device that vibrated the remote when you press a key to the touch and called it the Ultimate. Hence now the Touch is now called the Ultimate One.
X10 works great with my setup, I have been using Z10 for 20 years, the problem now is finding an IR-543 receiver to work between the X10 modules & Switches and your Harmony remote. X10 stopped making them a couple of years ago, and if you find any on eBay, you will pay a premium price.
IR switches are different from X10 switches, the IR switches have a IR window built into them and you only need to point your Harmony remote at them to control them, you don't need any type of adapter such as the IR-543 to control them.