In general, the threading on shower arms and shower heads are universal, they are all the same 1/2" threading. You can pretty much install any shower arm into the threaded union that is recessed inside the wall, and you can install any shower head onto the shower arm. There are always exceptions. But just look for the 1/2" threading. Valve trim kits? In general, they should be specifically matched to the valve body that is plumbed inside the wall. If you can identify the manufacturer of the valve and the specific valve model, that will be the best way to get a new trim kit that will fit.

We went with the Delta Lockwood for ours--we have the thermostatic control with regular shower head, the handshower with slide bar, an overhead raincan and the diverter. We can run each component by itself or in any combination of 2 or 3. I've listed a link below that will give you everything you need to know pretty much for setting up your shower with multiple components using a Delta system. Another option would be to use one of Delta's N2ition shower heads instead of the slide bar option. Hope this helps! Here is a link that might be useful: Delta Shower System Setup

Most designers design jobs with individual system components so they can build exactly what is needed. They rarely use “kits”. The price on those kits isn’t at all out of line for what you want though. I suggest that any faucets that you are considering be evaluated by reading Starcraft Builders Faucet Review site. If the brand isn’t listed, don’t even consider it. There are a lot of illegal imports into this country that don’t pass the required testing. But because there is no money for enforcement, they’re sold everywhere. Be very careful! http://starcraftcustombuilders.com/sources.faucets2.htm

Problem with a kit is the adjustability portion is done by the glass sidelites "overlapping". I would suggest custom as well. As noted above blocking needed to be installed prior to the tiling as well, typically.