Almost all of the three-rail ETS items you will find in the U.S. are fully compatible with U.S. tinplate operation, except for couplers. Numbers ending in B are supposed to have U.S. couplers, 3-rail AC wiring, and Lionel-type reverse (when the current is interrupted). Some have two-position E-units (no neutral) and others have regular three-position. The suffix 3AC-1 designates Marklin-compatible, with Marklin couplers and Marklin-style reverse on a 20 volt spike. These are almost never encountered in the U.S. A 3AC-0 suffix on the model number designates 3-rail AC with American-style E-unit, but with ETS hook-style couplers. The term "bogies" means the same as "trucks" in the U.S. I wouldn't worry too much about the "sound generators" as I've never seen one on a U.S.-market locomotive. You could probably order one so equipped directly or through their (not very active) American distributor.
There are complications. Most of the rolling stock with American-style couplers has U.S. style 4-wheel trucks, as opposed to the Euro versions with a single axle at each end. The short European cars look pretty strange with Bettendorf trucks. There are a lot of these around. You can get Lionel-type knuckle couplers to convert the Euro versions, but they are expensive.
Another thing to beware of on the secondary market is that few sellers actually know what they have, and the box markings are sometimes wrong, or the unit has been converted in some way. The only way to be sure what you have is to have it in your hand, or be sure the seller knows ETS. I have seen ETS locomotives listed on eBay that the seller didn't know if they were 2-rail or 3-rail, and they didn't post a picture of the underside. Caveat emptor.
You will also find ETS two-rail rolling stock and sets. The set locomotives that I have seen run on a rather exotic ETS proprietary control system that uses constant voltage, with frequency modulation to control speed and sound. I have one of the sets and the system works fine, but the 50-page instruction manual is in Czech and it is compatible with nothing. The track seems to be the same as some other European two-rail such as Fleischmann. I'm pretty sure ETS also makes two-rail stuff that runs on regular DC, with speed controlled by voltage, but I haven't actually seen any. The two-rail all has ETS couplers and scale flanges. The two-rail rolling stock will run on three-rail track, with the usual problems negotiating some switches. You can get hi-rail wheel sets to convert the two-rail cars, but they are a bit pricey.
The "tinplate era" couplers are English style with an upward-facing hook and a connecting link. If I remember correctly, the ETS version of these couplers will also connect to Marklin couplers. I think I have a pair of those around somewhere; if I have time I'll dig them out and post a picture.
ETS three-rail uses collector shoes rather than rollers. This is no problem running on tubular track, but the shoes will wear pretty quickly running on Gargraves or other hi-rail track because of the square corners on the center rail.
Personally, I prefer the ETS three-rail with hi-rail flanges, Lionel-type E-unit, and ETS couplers. I have some equipment with U.S. couplers and I've made up a conversion car with a U.S. coupler at one end and an ETS coupler at the other. I also have a Seetal Krokodil with a different coupler at each end. This actually has a homemade U.S. coupler conversion made by the previous owner. The factory U.S. type coupler won't fit this model. I have replaced all Marklin and English couplers on equipment I bought used with ETS couplers.
Here's a photo of one of my favorite ETS trains. The locomotive is a Garratt with U.S. couplers. You can see how the American trucks look under the short European-style cars.
The two cars on the top shelf are postwar Merkur. The gondola is a transition car; the front coupler appears to be a Marklin.
Here's another shot showing the ETS coupler. Note the buffers, which are removed on the units with American trucks. This car has a brakeman's shack for end of train use. Now this is the way to buy Pilsner Urquell - by the tank car!