Let's start at the beginning. Welcome to the forum. A good time to start - lots of time to read up and, hopefully, to get at least part of a beekeeping course under your belt.
Presumably your flat pack hive is a standard, not a jumbo (which is also called a 14 x 12 and has frames which are 12 inches deep). Standard is 8 1/2 inches deep.
A really basic hive would comprise floor, brood box, coverboard and roof. Normally they come with one or more 'supers' and a queen excluder.
Over the ninety-ish years since the standard was drawn up (until then components were often incompatible between hive formats, so the standard was set for simplicity of manufacture - from the compatibility angle) strains of bees kept have changed and generally become more prolific with regards brood size. The two common boxes used were, and are the 'standard' (for the brood) and the 'super' or 'shallow' for the honey surplus.
The popular option, for larger colonies, used to be that of using a brood box and a super for the queen to lay in. Called a 'brood-and-a-half. More recently some have moved to the even larger size of double brood - two brood boxes. Even more recently the 14 x 12 'jumbo' option has become much more popular and has a brood area of approx. 1.7 times that of the standard brood.
So there are basically four different options and all need consideration from the angle of which strains might be housed, while being big enough but not too large. There are other options of course; I run 14 x 12s but often allow the queen to lay in a super (during the springtime, in particular); some find they need 3 brood boxes to contain the broodnest, but these are a minority at the present time.
So to your question. The standard box is usually used as a brood only. A few do use it as a super but as others have said, it is vey heavy when full. Another downside is extraction of these larger frames - there are no so many radial machines (the prefered option for most these days) which will take these larger frames. So they are usually extracted using a tanential machine which rather slows down the process. I would think also anyone using a radial machine for extracting the larger frames would have to be much more careful (extra wiring reinforcement?) as the combs are subjected to consideable force and even some of the smaller framed comb disintegrates during extraction.
Double brood if preferable to many (over a brood and a half), these days, as frames are all the same size and can be used in either box, making some manipulations so much easier. 14 x 12 frames are popular because only a single box is used, so fewer (but heavier and more fragile) frames need checking (but there are other advantages too).
Large supers are a bear if they are not filled completely during a flow. For instance, OSR needs to be extracted soon after the flow (or it granulates). Generally only full, capped frames are extracted and smaller are handier from that angle. They are also less handy if they are needed to be drawn out by the bees in cooler weather. Many beeks over-winter their full colonies on as brood and a super of stores, which is more than adequate for most winters (also equates approximately to the 14 x 12). Some strains are overwintered on double brood, but unless they are a really large colony, there are downsides such as unused sugar syrup possibly finding it's way into the honey crop. So lots to consider for your particular set of factors. The above may not even be exactly what you were meaning in your question.
Hoffmans throughout? Yes. But there are better choices for different conditions, some would say. If you choose to use one box size, then the same frame throughout the hive is a sensible choice.
I would opt for a single brood for your first year and a shallow super. That may be dependant on when yor bees arrive, but you should not expect a huge crop from a late nucleus - if you get any, you may be doing well. It depends on lots of things again. Yes, you can get a really prolific queen and get a good surplus from an early nuc, but beware that the queen may not over-winter as well as you might have hoped, so may, ideally, need replacing in the autumn - not the sort of thing someone with only one colony should be contemplating, especially in their first year.
Beekeeping is easy but not simple!
Regards, RAB
PS a lot of this may by now be out of date, already covered by posts above; but my cr*ppy ISP keeps failing, connection-wise (aol).