MMM should be able to find anything under the VST folder.
I have another VST instrument.that installed itself elsewhere. Rather than move anything, I just added the path under VST paths:
You also mentioned that you found it strange that the other instruments are elsewhere. The Magix instruments were not real VST's or something like that so they behave differently and are located elsewhere. I think that Magix is, has or will be changing these over so that all of their instruments behave like VST's. This will simplify things. I read this somewhere on the Samplitude forum.
Samplitude Pro is the top, or almost, and can be quite complicated.
You may have received Music Studio with Music Maker. It is a very light version of Samplitude Pro. The next up after that is Samplitude Music Studio. They are all very similar in look and feel. The big difference between them and Music Maker is that you can record to more than one track at a time. Next, I would say that you have more flexibility because you can change the BPM as you go along. In MMM, the BPM is set for the entire composition, I believe. Thus you may want to take a look at Music Studio.
Can you get back and tell us if EZKeys works as desired in MMM?
As per your PM about 32 and 64 bit plugins, the VST's go into different locations.
32: C:\Program Files (x86)\VSTPlugins
64: C:\Program Files\VSTPlugins
Music Maker is not yet 64 bit, but the next version will probably be. Thus you should always obtain both 32 and 64 bit versions of plugins, if there is no extra cost.