I think the two best producers in rap ATM are Atlanta producers - Metro Boomin and MikeWillMadeIt (although Metro was born and raised in Missouri and MWMI was from outside Atlanta, though from Georgia). The connection between these two (not to mention Southside/Luger et al) is Brick Squad - OJ and Gucci Mane. Interestingly, looked up Luger and he's from Virginia, and Zaytoven was born in Hamburg, moved to San Francisco, but came through in a big way working with Gucci in Atlanta - I suppose Atlanta must be a magnet for producers and rappers - and Wiki confirms my vague suspicion that it's a magnet for black americans generally:
WIKI: 'Atlanta has long been known as a center of black wealth, political power and culture; a cradle of the Civil Rights Movement[1] and home to Dr. Martin Luther King, Jr. It has often been called a "black mecca".'
Also useful is the Wiki on Atlanta hip hop
In 2009 the New York Times noted that after 2000, Atlanta moved "from the margins to becoming hip-hop's center of gravity, part of a larger shift in hip-hop innovation to the South." Atlanta hip-hop’s pop breakthrough—everyone from Jermaine Dupri to OutKast to Lil Jon—involved the blend of various distillations of hard-core sounds from the West, bass beats from Florida, and styles and images from the North.[8] Producer Drumma Boy called Atlanta "the melting pot of the South". Producer Fatboi called the Roland TR-808 ("808") synthesizer "central" to Atlanta music's versatility, used for snap, crunk, trap, and pop rap styles.[1] The same article named Fatboi, Shawty Redd and Zaytoven the four "hottest producers driving the city".
Didn't even think about how Lil Jon was from Atlanta...
I would guess that this melting pot cosmpolitanism partly explains why you get characters like Andre 3000 coming out of Atlanta, and why Atlanta seems to be at the forefront of this dyed-dreadlock generation of flamboyantly dressed rappers. (Young Thug as an Atlantan spin on Lil Wayne.)