I am not with Laminar Research or X-ForcePC; just a flight simmer from downunder.
In response to your second (last question) you need to ensure you install the components through X-Plane. No other way. Don't contemplate using the software supplied with the components and not even through your operating system. Although it may work with other "shootem-up" gaming packages or flight sim packages will most likely experience operating problems.
In response to your first query I am of the opinion that, unless this is where just X-Plane will reside, the size of your SSD will not be large enough. Have a look at the following links from Michael Brown. Michael runs a company (XForcePC) in the USA which is recommended by Laminar Research as the PC supplier for X-Plane.
Have a look at the following video at https://www.youtube.com/watch?v=gJOgpZVjXoU . Consider the message regarding single drive storage capacity and additional drive storage capacity.