Gday (insert name here), welcome to the ANZLF.
Planning is a very important part of the build as far as process goes. But if you are talking design aspects, they should remain open enough to apply new ideas along the way or to accommodate the unexpected. Some of the best 'highlights' I have seen had been the result of an adaptive builder covering up an error. So that takes care of questions one and two because as a beginner, you simply 'must' be prepared to go back and change things as there are just too many things that can and probably will go wrong along the way.
Basically speaking tonewood grading is much like anything else. The right choice for most lay somewhere between two extremes and comes down to what is visually acceptable and functionally desirable to the individual, divided by how much money they have to spend that determines 'their' best choice. Once a decision is made, it is then a matter for the builder to get the best they can from that choice. So if you consider the extremes, best to worst, it can help give some idea of what should work for you and your budget.
A 'master' grade top is not going to sound any better than a "AAA" or even a "AA" grade top, but it should be aesthetically perfect which is a rare thing in natural products like wood. So just like any other collector of rare beautiful things, you will pay very dearly for such an exclusive commodity....but being rare to the eye is 'not' a property in itself that is going make an instrument 'sound' any better. It does not make the wood stiffer or lighter, it just looks 'nice' and nice is good if that is the 'look' your after. That said I find it impossible to see how anyone just starting out could ever justify using master grade anything.
The other extreme is "A" or even "B" grade wood. I group them together as it depends very much on who is grading, but the real indicator is price, if wood is very cheap, there is usually a good reason why. Now some of this stuff can be just fine,
"as long as you have the experience to pick through and identify something that is 'structurally' worthy of the time and effort you will invest when turning it into an instrument" If you do have that experience then you can get away with some pretty 'rustic' looking tops that fit the bill just nicely if you will be painting or staining the top, or are after a warts and all 'woody' look, and you will also save a lot of money.
But once again I find it impossible to see how anyone just starting out could justify using "B" grade anything. Their lack of experience would have them gambling that their choice has not left them with a top that not only 'looks' a bit dodgy, but is so floppy that it simply cannot be braced to function effectively, or, so full of short grain that the bridge flies off the moment it is placed under string tension ripping a gaping whole in the guitar as it goes. My best advise is to only buy from a reputable tonewood dealer who grades according to industry standards, and buy their "AA" grade requesting light and stiff with least runout over the best looking of the bunch.
Bending, I do not see any real 'advantage' of a pipe over a blanket but suggest you be prepared to set up with both if you intend to build a few instruments. The blanket and form are the go to for bending sides and bindings, but a pipe is great for touch up work that may be required because of spring back, and also for doing the little bits and bobs you come across on headstock bindings, headstock backstraps and fretboard ends etc.
Cheers
Kim