Sorry for "necro-ing" an old thread, but I was about to post basically the same question, and this came up on the list of suggested prior posts (which is an awesome feature for a forum, btw!).
I recently played with the defaults (50% and 15, I believe) and set minimum connections for Sol to 5, and I can't say I love the resulting map. It's basically a five-armed star, with each arm occasionally branching, all centered on Sol. The five arms do not interconnect at all; to get from one to another, you MUST go through Sol. I started a test game with parameters set to 90% and 15, and after using Spacemaster to explore 27 systems, got a map that I like a lot more, copied below. However, testing it one more time, I got a map that was less loopy and much more standard branching with minimal to no loops.
I can't make sense of the first parameter, either, since with my settings it seems to imply a 90% chance of linking to an existing system (within the last 15 systems generated), but I'm not seeing anywhere near that number of links back to existing systems. I assume that would then give a 10% chance of linking to a "non-local" system, i.e. one more than 15 numbers away from the one just discovered? And does this apply to each jump gate explored?
Has anyone else experimented with these, and can you share what parameters you used and what your map looked like as a result?