It's a pretty diverse place. Some profs will lean more heavily into theory and concept-driven design - other profs are very technically demanding and you'll need to become technologically proficient in some of the most niche tools in the industry (i.e. CATIA, Unreal Engine, augmented reality, fabrication through robotics). 

Just over half of the school faculty is practicing architects with built projects to their name (and most of which aren't your regular buildings but ones that needed advanced technologies and political/social maneuvering to get them done). It's actually not that common for schools to be practicing architects. That being said there is definitely a side of SCI-Arc that claims "architects don't need to build buildings" and steer students into Hollywood or product design or even fine art. It's the kind of school that can accommodate both opinions so you can pursue what you want  

The courses on offer and environment caters best to people that don't really care for what's "typical" or normative - the firms and companies that are linked with the school share those same attitudes. 

To answer your second question: No, In hiring situations for architectural practice, I have never seen anyone look askance at an  MArch I background vs. an MArch II.   The name on your degree is a much bigger deal.  Rightfully or not, employers fall all over themselves to hire grads of Ivy League and few other "prestige" architecture grad schools.

Regarding your third question: There are many other M.Arch I programs in the United States that accept students with all kinds of undergrad degrees.  I suggest looking at some other schools to better understand the options out there and how they compare to SciArc. 

Also avoid any program where you will have to take out big loans to pay for it.

First, do you really know what the profession is like? Check out this video

So you want to be an architect

I have heard sci-arc uses a lot of digital tools to create those weird models. Those weird stuff may be fun but will not really help you in a traditional architecture firm much. But at the end, none of the architecture schools will turn you into architect, you will always have to start from the entry level to learn and climb. As long as it is NAAB accredited school it is good. The rest is really on you to show your work on portfolio. The only difference between grad schools is really just ivy league tier master programs for their name. If you cannot get into those, just go with a typical cheaper graduate school that is NAAB accredited for less debt.

It is a hotly debated school, with a very strong style factor. However, I work with several former students from there who mostly seem about the same as anyone else from any other school. The reality is that they have a higher portion of students that do not actually go into the field of architecture than many other schools, but that’s a personal choice often related to the sort of people the school attracts. Ultimately, the opinion of the school is probably well balanced, because some people hate it, some people love it, and a lot of people just think it’s another school.

As mentioned above… the MArchI won’t matter. To clarify though, the degree will just be a Master of Architecture... you'd never put the MArchI or II on your resume.... and if you did, I always like to point out that these do not have defined meanings, so they change per school.

There are a lot of options for you at other schools. They won't all be called an MArchI (per my comment above)

I second the debt comment. I would say this is my only real problem with Sci-Arch.