actualy, its the first 2 if you're being honest since i dont assume anyone here has a real reference for mastering. The thing that GS always has done is discuss high-end gear and make cross-references, these are mostly pro's and makes GS an interesting site for bedroom-techies. Along those lines you will learn that paid engineers explain which facets are beneficial for either mixing, recording and/or mastering.
Yes but like I said, generally we dont have pure mix engineers. We have people that mix tho. It also comes down to what people call themselves, but Im pretty sure, out of the Hundreds of thousands of members, most identify with producer. Like I said, there are exceptions to every rule, and alot of cross over, as all jobs are needed to complete a thorough project in any genre, but its what people identify with.
ie. I myself mix, I love it and Im pretty good, but I wouldnt identify with the title mix engineer. I dont do engineering as a stand alone activity. I do it exclusively within the realm of production.
On GS, you have people that do it exculsively. Not to mention, you have people that engineer for fucking Kanye West, Tupac, and alot of other 90-2011 CLASSIC artists. Theres overlap, but the two sites serve two completely different crowds
Which answers the rest of your post also.
The requirements for recording and mixing dont compare to those needed in mastering. I suggest to read more on GS and if you want to go that route, absolutly cool...just get ready to pull out the wallet and a toolbox.
Absolutely, I still encourage people to learn mastering techniques. Knowledge is leverage, money, and power. Just dont expect to be in the million dollar studios, with million dollar equipment, churning out million dollar mixes lol