lets address the issue with river aesthetics, which is to say, most rivers occlude existing terrain and force flat plains for the surrounding tiles. resulting in river embarks that are mostly uninteresting, 'regular,' experiences, with few of the more exceptional geological formations one can find.
===
to overcome this, become familiar with understanding topology through the world map two functions 'Show elevation' and 'Show cliffs/grade.'
These tool overlays produce certain recognizable artifacts which can be manually hunted down. See as follows, imagining a 2x2 embark in each of the highlighted red circles:
Default embark view:
(https://i.imgur.com/n5WtXv9.png)
please note how the world map graphics imply certain terrain features, like mountains.
Show elevation:
(https://i.imgur.com/ZirSJkF.png)
consider each highlighted spot in turn:
1. blue into green suggests lowland terrain, swampy, lots of aquifer. the sharp contrast suggests moderate cliffs
2. three sharp contrasting elevations together suggests complicated cliff terrain. the nearby waterfall would also add to the variety here
3. boredom ensues as there are no cliffs to be seen, as indicated by a solid chunk of green
4. again, no cliffs here. note how the default view suggests mountains
5. AGAIN, no cliffs here. no interesting terrain. and AGAIN, default view suggests 'mountains'
6. Here, we have massive cliffs running up west to east.
7. More cliffs, with a waterfall. The same triplicate elevation is seen.
Show cliffs/grade
(https://i.imgur.com/P7vaURt.png)
1. Yellow confirms moderate cliffs
2. solid red flanked by a thin green line indicates river waterfall
3. this suggests orange cliffs, but in my experience they would require a 4x4 or larger embark to even perceive on the map...
4. again, suggested cliffs, but the center 2x2 embark would see only a small portion of this terrain
5. same as above, the features are only present outside the river's path
6. no new info
7. no new info
Let's look at some more specific and quirky examples, using these overlays.
Oceanside Mountains:
(https://i.imgur.com/oYsMIyJ.png)
1. looks fairly boring on default view, yet elevation reveals a complex riverside cliff
2. seaside cliffs, due to the intersection of lowlying biomes and highlands. super fun style of embark
3. must use 'embark anywhere' which I'm not sure is available for premium? anyways, this would be an epic cross-fjord bridge location, as indicated by the high contrast blue-dark orange.
winding river valley full of waterfalls:
(https://i.imgur.com/t0PRCkI.png)
indicated by the contrast between light blue river terrain and the dark orange of the plateau, each intersection here represents a potential for interesting cliffs and river interactions.
super low terrain due to a river loopback:
(https://i.imgur.com/iHRdCU0.png)
Something about the generation of the world, not sure what, results in super low lying rivers next to oceans that often extend this low elevation deep into continents. In this case, that shallow ocean river has collided with itself after turning, resulting in a potential 4x4 embark that accesses a huge north-south variation in terrain. This would probably be a great place for a castle..
So there are two principle takeaways from this:
First, the default view lies to you (it always has) in the way it presents biomes before terrain. Mountains are not 'mountains' but regional intersections of temperature, humidity, elevation. . thus you need to see past these biomes to truly perceive what literal shape your embark will take.
Second, you should be prioritizing your hunt for quirks in the generation. Places where too many features occur for it to all generate 'correctly,' thus producing oddities like cliffs next to oceans, or lakes that fall out of the sky. These are super fun and most people don't even know they can be actively, even easily, discovered.
if you simply want a world with a lot of small, winding rivers that intersect terrain frequently, with potential for bridge building / super tall towers, check this worldgen 'Varied Heights 500yrs'.
[WORLD_GEN]
[TITLE:VARIED HEIGHTS 500YS]
[DIM:65:65]
[EMBARK_POINTS:1504]
[END_YEAR:500]
[BEAST_END_YEAR:200:60]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:2600:2600]
[RAINFALL:0:100:200:200]
[TEMPERATURE:25:75:150:150]
[DRAINAGE:0:100:150:150]
[VOLCANISM:0:100:150:150]
[SAVAGERY:0:100:150:150]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[POLE:NORTH_AND_OR_SOUTH]
[MINERAL_SCARCITY:1000]
[MEGABEAST_CAP:20]
[SEMIMEGABEAST_CAP:40]
[TITAN_NUMBER:50]
[TITAN_ATTACK_TRIGGER:4:0:4]
[DEMON_NUMBER:22]
[NIGHT_TROLL_NUMBER:11]
[BOGEYMAN_NUMBER:11]
[NIGHTMARE_NUMBER:11]
[VAMPIRE_NUMBER:50]
[WEREBEAST_NUMBER:50]
[WEREBEAST_ATTACK_TRIGGER:3:3:3]
[SECRET_NUMBER:44]
[REGIONAL_INTERACTION_NUMBER:22]
[DISTURBANCE_INTERACTION_NUMBER:22]
[EVIL_CLOUD_NUMBER:22]
[EVIL_RAIN_NUMBER:22]
[GENERATE_DIVINE_MATERIALS:1]
[ALLOW_DIVINATION:1]
[ALLOW_DEMONIC_EXPERIMENTS:1]
[ALLOW_NECROMANCER_EXPERIMENTS:1]
[ALLOW_NECROMANCER_LIEUTENANTS:1]
[ALLOW_NECROMANCER_GHOULS:1]
[ALLOW_NECROMANCER_SUMMONS:1]
[GOOD_SQ_COUNTS:6:63:127]
[EVIL_SQ_COUNTS:6:63:127]
[PEAK_NUMBER_MIN:3]
[PARTIAL_OCEAN_EDGE_MIN:0]
[COMPLETE_OCEAN_EDGE_MIN:4]
[VOLCANO_MIN:3]
[REGION_COUNTS:SWAMP:66:0:0]
[REGION_COUNTS:DESERT:66:0:0]
[REGION_COUNTS:FOREST:264:0:0]
[REGION_COUNTS:MOUNTAINS:528:0:0]
[REGION_COUNTS:OCEAN:528:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:528:0:0]
[REGION_COUNTS:HILLS:528:0:0]
[EROSION_CYCLE_COUNT:40]
[RIVER_MINS:22:22]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVERN_LAYER_COUNT:3]
[CAVERN_LAYER_OPENNESS_MIN:0]
[CAVERN_LAYER_OPENNESS_MAX:100]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:100]
[CAVERN_LAYER_WATER_MIN:0]
[CAVERN_LAYER_WATER_MAX:100]
[HAVE_BOTTOM_LAYER_1:1]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:15]
[LEVELS_ABOVE_LAYER_1:5]
[LEVELS_ABOVE_LAYER_2:1]
[LEVELS_ABOVE_LAYER_3:1]
[LEVELS_ABOVE_LAYER_4:1]
[LEVELS_ABOVE_LAYER_5:2]
[LEVELS_AT_BOTTOM:1]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:6]
[NON_MOUNTAIN_CAVE_MIN:12]
[ALL_CAVES_VISIBLE:0]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:60]
[TOTAL_CIV_POPULATION:10000]
[SITE_CAP:264]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:528:1056:528]
[RAIN_RANGES:264:528:264]
[DRAINAGE_RANGES:264:528:264]
[SAVAGERY_RANGES:264:528:264]
[VOLCANISM_RANGES:264:528:264]
there are various other changes but the big ones are the super low erosion cycle count of 40, and 5000 possible subregions. you will not find super large rivers on this world, however, you will find oceans that act like rivers haha. . 'fjords' is perhaps a better term.