I have a few questions about choosing joint compound for taping sheetrock
walls. I also have a question about "plaster".

For taping sheetrock walls:

I know there is "regular" pre-mixed and "lightweight" pre-mixed joint
compound that comes in 5-gallon buckets. I can easily see what the prices
are for those products at Home Depot, Lowes, etc. I have used both of
these, so I have a pretty good idea of how they each work. One issue I have
with them is that they take so long to dry between coats -- sometimes 24
hours, sometimes longer if they are used to fill thicker gaps. And, they
both tend to shrink and crack when used on thicker gaps.

I also see bags of dry "setting type" joint compound with varying setting
times such as 45, 90, etc. I can, of course, see the prices for each bag.
But I can't tell how many bags it takes to mix up about the same amount that
a 5 gallon bucket of pre-mixed joint compound contains -- so I can't tell
how the dry-mix prices actually compare to the pre-mixed prices. Can anyone
here give me an idea of how the two (dry-mix setting type and pre-mixed)
compare in terms of cost for the same amount of product -- such as per 5
gallons of useable product?

And, aside from cost, has anyone decided to just go with the dry-mix setting
type joint compounds even for large jobs simply because it dries and can be
re-coated in so much less time? Also, the dry-mix setting type product
doesn't seem to shrink when drying which is a plus for me. I don't mind
doing the mixing etc., but I never saw a contractor using the dry-mix
product so I wonder if there are disadvantages or reasons why using the
dry-mix is not generally recommended for most taping jobs.

And, about "plaster":

I seem to recall that I used to be able to buy actual plaster at places like
Home Depot and Lowes, but I don't see that there these days. And, I thought
I used to be able to buy the "rough coat" ("brown coat") product that goes
on underneath the finish coat of plaster. By "plaster", I mean the actual
finish coat plaster that old time plasters use for plastering entire walls.
I think the plaster was called "finishing plaster" or "finish coat plaster"
and not Plaster of Paris, but I don't know for sure. And, the finish coat
plaster dried fairly slowly but did not shrink and dried to a very hard
finish. Am I correct that there is a product out there somewhere that is
called finish coat plaster, and that is not the same as Plaster of Paris?

Any info or suggestions regarding all of the above would be appreciated.