The Smart Mirror can only work with one assistant at a time. This is because it allocates Port 3000 on the Raspberry Pi for listening. Due to this trying to run multiple voice assistants will not work. It is better to choose one that you commonly use and integrate that with the Smart Mirror. (I have both Google Assistant and Amazon Alexa running on my Raspberry Pi but only one of them can be used at a time).
Many of the modules used with my Smart Mirror project may not work after a point of time as Google and Amazon and other resources that provide data to the different modules of the Smart Mirror may update their interfaces and other integration properties. Therefore it is best to constantly upgrade the packages.
However upgrading the packages may cause some of the modules to stop working as not all of them are capable of handling the newest version of the software. For example in my case, Google Assistant runs smoothly only on npm version 5.8.0 and above. While the Smart Mirror is optimized to work on npm 5.6.0 .
While building the Magic Mirror it is better to use a two-way acrylic mirror rather than going for a glass Mirror as it may crack/break if not used carefully. In my case the glass cracked and I had to replace it with and acrylic sheet covered with a reflective tint at the last minute which in turn reduces the quality of reflection and reduces the brightness of the display screen used.
It is very important to make sure that light cannot pass through the rear of the two-way mirror, as this will cause it to act like a clear pane of glass as reflections will very hard to see. A quick and easy solution for this can be to use some black paper/ black wrap that can block most of the light.
Finally to design the mirror its best to use a large monitor with good brightness properties to ensure best viewing. If using a smaller monitor like me, you will quickly notice that you run of screen real estate. In my case as I wanted all my modules to be displayed at the same time rather than having different pages. Therefore using a larger monitor would have been more efficient.