Oooph, long questions, even longer answers? :lol:
In the forum here there is enough said about hardware - no need to go into it again.
So only some general remarks (based on my gut-feeling mostly).
4GBs is not too great, you might think about upgrading.
Most people seem to prefer GForce vs Quadro - you get much more power for the buck.
No idea.
I guess there are a lot of software developers trying to figure that out, too! 
One significant difference is that you don’t have manual influence on the alignment process or rather you cannot optimize it.
In most cases it is ok, but in others it would be a benefit.
I have found that there are so many different factors involved (camera, object, photographer, to name but a few) that there is no general answer as to which software is better. You just have to try out what suits you best.
In most cases I personally get better results with RC, also because its hardware requirements are much better - with other software I would never be able to do anything as complex as with RC. Only few cases made it necessary to use other software.
Wow, that seems like a lot of effort for your purpose - I am a trained architect myself.
It does take quite a bit of commitment to get really good results, but that is true for most software.
In contrast to marketing, it isn’t just about taking a few images an - bling - you have a beautiful flawless model.
You need to learn to navigate the difficulties and most important how to take proper images.
Believe me, I am working on and off since 1.5 years with RC and not even close to being routined… :shock: