Hey Stimmy, welcome to the forum. Good first post!
What material to use on what fly pattern can be really confusing. And of all materials hackle is probably the most confusing--- it can also be very expensive.
This forum is a great place to ask if you have questions about materials--- just let us know what you're tying and folks can point you in the right direction. After awhile you'll get your head around different materials and their qualities and uses in different types of patterns. But getting back to hackle...
... The key qualities of hackle are barb softness/stiffness and length of the individual barbs. (There are other important qualities as well including flexibility of the stem, the overall length of the feather etc.)
Barbs that are soft and webby are used on wet flies and streamers. Hackle with stiff barbs are used on dry flies.
And all hackle isn't created equal--- some have short "soft" "webby" barbs that are used for wet flies like soft hackles and winged wets. These are often from game birds like partridge, starling, or from (chicken) hen capes.
Some patterns like woolly buggers in hook sizes 8-12 use hackle with longer soft webby barbs. These are usually rooster saddle feathers referred to as bugger patches or bugger saddles. Strung hackle can also be used, but the barbs tend to be longer and are more suited for larger hook sizes.
When referring to dry fly patterns, hackle refers to genetic roosters bred especially for their dry fly quality hackle- thin flexible easy to wrap stems and stiff barbs of uniform length. These feathers are considerably more expensive than the imported strung hackle which are feathers from birds raised for their meat.
Both capes (also called necks) and saddles from genetic birds can be dry fly quality, with some breeders like Whiting strong in both. Other breeders are stronger in capes. These can be expensive, and are usually sold in different grades. Many companies that sell genetic hackle (Metz, Conranch, Collins) use a 1,2,3, grading system. Whiting red label products and Whiting Green label (their Hebert Miner line) use Gold, Silver, Bronze, Pro Grades. Whiting 100’s are made from saddle feathers, and a pack will tie approximately 100 flies in one size and one color for about 18.00
Here’s a link to an old thread that might help:
Rooster Necks vs Saddles Uses, and Selecting from a Neck
Keep asking questions, I'm sure for every one you ask there are several others out there with the same ones.