McJeff-
There are quite a few different things that give beer it’s mouth feel. Proteins, Alcohol content, amount of carbonation, etc… but the thing that will most contribute to the beer’s mouth feel, whether it is a crisp, clean pilsner or a thick, viscous stout is the quantity of unfermented sugars left after fermentation is “complete”. You see, often beer yeast will “poop out” and not consume all of the fermentable sugars. Other times, there are sugars that the yeast just can’t consume, like lactose or Maltodextrin. These leftover sugars (some taste sweet, some do not) can make the beer feel “heavier on the tongue” or thicker or more viscous.
Pellets vs Whole hops-
Here is what I have found. Pellets typically store better (last longer all things being equal). They add less “vegetable matter’ to your wort (which can be a good or bad thing depending on your beer style). They also settle out faster in the kettle and the fermenter, and are generally less of a PITA when siphoning (don’t clog your tubing).
Whole hops when fresh I think add a more complex flavor and aroma profile. They are also useful for mash hopping (adding hops to the mash) and help with lautering in the grain bed- although no many people do this. Also, whole hops take up more space to store and in the kettle. They also absorb more water in the boil kettle so you need to adjust the volume accordingly.
As far potency- the Alpha Acid (AA) content should be printed on the package. All else being equal, if the AA content is the same, then you can use either one ounce for ounce/ gram for gram.
When you boil hops a lot of things go on, but most importantly, you isomerize the AA in the hops- that is, in lay terms, you make them bitter. The longer that you boil a hop the more bitterness that you extract (to a point). The amount of potential bitterness is affected by the gravity of the wort- all things equal, the higher the SG of the wort, the less bittering that you get per ounce of hops. Dry hopping only adds flavor and aroma.
Length of time in the wort (or must) is dependent on how much bittering/ flavor/ aroma you desire. There are many calculators available online that can assist you- just google “IBU Calculator”. For dryhopping one week is typical- two weeks max.
Average hops per gallon will vary greatly. For my Oktoberfest, I only use 0.3 oz/ gal of a low AA hop for a total of about 25 IBU’s. For a double IPA I use over 2 oz/gal for around 100 IBU’s. It all depends what you are going for. Keep in mind that IBU “feel” in beer don’t exactly translate to IBU’s in mead… there is a lot of other “stuff” in beer that can make the bitterness more or less intense.
IBU Calculator:
http://www.brewersfriend.com/ibu-calculator/
Hope this helps