Before I answer your questions, I would like to share what my educational path/experience has been, so that any biases I may have that I do not see become apparent to the reader. I will try to answer the questions from my own personal perspective, rather than from a meta-analysis point of view:
K-1 Homeschooled
2-9 Public School
10-12 Homeschooled
During grades 4-6 I attended two schools simultaneously, (two days a week at one, three days at the other).
The three day class was your typical public school environment with the caveat that I was also in all the available advanced coursework classes, so they tended to stay a bit smaller than your average classroom size.
The two day class was a much more intimate affair with advanced curriculum and smaller class size (between six and eight students).
Beyond public school, I have attended three years of private university in my spare time. I am still currently enrolled. Class sizes vary from 10-30 students.
1) Is homeschooling better for introverts than public schooling?
In general, yes, if you are referring to actual learning. There is the issue of social awkwardness that comes up often regarding my time in homeschool, but it is largely a moot point. I find that I can carry a conversation with a more diverse group of people better than similarly tempered individuals that are my peers. In public school, I fared better the smaller the class size. Even today while attending university, I find that I get much more out of a smaller classroom setting than that of a larger setting.
2) Can too much social interaction negatively affect academic success for an introvert in the classroom?
I find too much social interaction draining. It's like a bad sugar buzz that doesn't wear off, and when it does, crash time. It's very distracting. My wife (INFJ) has a knack for knowing how many people were in a class just by my actions when I get home from a class. The smaller the class, the better I think most introverts will perform.
3) Do introverts always work more effectively independently vs. groups or teams?
I think most introverts prefer to work alone, or if they must, in smaller teams. Personally, I loathe working in groups, because two things will always happen: 1) I will get stuck with the lion's share of work, because I know it will get done that way (I am a duty fulfiller), and 2) I will get stressed out because of this, because I know that my work will be critiqued by my peers and not just by the professors, so I will pull all stops out to try to perform at an even higher level.
Did I mention I hate working in groups?
4) Do introverts learning style different significantly from extrovert learning styles?
I cannot answer this directly, as I an not an extrovert. I offer this additional anecdote, however: When my parents made the decision to switch their children (myself included) back over to homeschool, they left my extroverted brother in public school, and only pulled out my sister and myself. My sister is also, to an extent, introverted.