If you like the MS854114S Original Ultramax, you would likely very much like the Ultramax II, which looks a smidge more modern and has a dual-cyclone flush, an ADA height bowl, and Sanagloss all standard. It's MS604114CEFG -- look it up -- and you will find that it is actually comparable in price even though it has all these extras.
The Swash should fit the Ultramax and Ultramax II. But get some input on here from folks who have actually used the various bidet seats. Terry sells a fair number of them and is a great resource about them.