These worlds have eight gates and are more likely to have off-world contract through the gates.
An Alt visited enough may become a Prime.
There is no discernable logic to the placement of Primes and Nodes within the Fringepath System. A World of Magic may reside next to a world of Hard Science.
Primes are game worlds that the GM knows well and in large detail - the primes will influence the flavor of the game for a long time.