I typically play with 12-15 civilizations and 24-32 city-states. The map script doesn't alter rift placement based on civ count, but resources and hills are added as needed to balance starts.
I've tried tweaking the map script quite a bit and I'm narrowing down what I'm looking for to a few things:
Without using rifts (they look like they need a major re-write to address my concerns with them):
1. Increase the amount of trees and especially jungle on the map. -Done
2. Reduce the visible banding of trees and terrain types at transitional latitudes a bit, so there's more variability around the 3 or so tiles north and south of the latitudes where tile types transition. This is basically de-prioritizing latitude while emphasizing "weather". -Done
3. Reduce the number of 1-3 tile islands in what would otherwise be ocean by about 25% (mostly to decrease the amount of navigable waterways prior to ocean travel. -Major task
Reading over the map script, I don't see anything that appears to control for 1-3 tile islands. Rifts are a relatively easy way to hack the map to create ocean divides, but I'd hope to push the map towards a slightly more elegant solution. What I'm looking for is something akin to Indonesia (multiple 1-3 tile islands connected by coastal waters to each other and to a larger land mass in 1-3 places on the map, with other 1-3 tile islands scattered with ocean between them and major land masses. The intention is to limit early exploration off the starting continent.
Step one would be to simply remove land tiles from islands that share shallow water with a continent, until X% of islands are not connected to continents. Step two would be to identify archipelagos that still have a coastal connection to a continent and buff them a bit with additional land tiles and islands, but in such a way that the archipelago only connects to one continent by coastal waters. An Archipelago connecting two continents would have the island tiles remove from close to one continent until that coastal connection is removed.
I read the entire Communitas .lua this afternoon and made a few changes which I'm attaching:
-Increased tropicLatitudes from 22 to 27 gives more room for both deserts and jungle.
-Increased horseLatitudes from 23 to 19 gives more room for plains. The idea with these two is that some overlap might generate more variance around the latitude transitions. I'm not sure if it worked exactly, but the result seems good.
-Reduced landMaxScatter from 0.06 to 0.04 in an effort to reduce islands. This is one change I'm not fully set on, but the results are generally ok if not very effective at reducing islands.
-Reduced coastScatter from 0.09 to 0.05 for the same reasons landMaxScatter was reduced.
-Reduced BelowMountainPercent from 0.94 to 0.92 for slightly more mountains.
-Reduced hillsBlendPercent from 0.45 to 0.35 to compensate for having more mountains on the map.
-Increased featurePercent from 0.60 to 0.75 in order to add more jungle and forest in general within the allowed areas.
-Reduced zeroTreesPercent from 0.35 to 0.20 to allow for more trees in general
-Reduced plainsPercent from 0.50 to 0.40.
-Reduced desertPercent from 0.67 to 0.60 to allow more room for jungle (jungle doesn't like being near desert).
-Reduced riverPercent from 0.25 to 0.23 to remove some of the one-tile rivers that are very common along the edges of continents. Might reduce this further to 0.22 but it seems to be very sensitive.
-Increased riverRainCheatFactor from 1.25 to 1.45. This apparently increases watershed area, and I was happy with the resulting longer rivers. Adjust this up to 1.65 if riverPercent is adjusted down to 0.22.
-Increased geostrophicFactor from 3.0 to 5.0 to increase the impact of weather (monsoon climate) over latitude. I think this had a big impact, and I haven't yet tried values other than 5.
This map is intended to be used without rifts. I played around with rift values and decided some more significant work is needed if they're to be very good. Specifically, I'd want to add vertical variance in the sin calculation for the Atlantic rift, rotational variance for both rifts, and the option to specify different widths at the "top" and "bottom" of each rift. These changes require more research, and I'd prefer the archipelago solution outlined above instead.
Here are some screenshots of a sample map:
Overall there are large landmasses but not enough separation between continents.
Continents have large deserts as well as thriving forests and jungles:
The elongated river watersheds create distinct geographical areas:
Notice the very wet area near my spawn, with many rivers, jungle, and marshes filling up this desirable area:
I recommend playing this map script with no more than 14 civs and 28 nation-states on Huge. I play with the City-States Evolved mod though, so you might be able to increase the nation state count slightly without it.
Editing to add that my changes do go against the original intent of this map, which is to create an Earth analog. My map has wider ranges for jungle and technically there should be a lower percent of land than this map has. It's also much wetter than Earth imo.