i meddle with txt file all the time.
normally i ajust with river start position, erosion cycle and sometimes with peak/volcano numbers.
or volcanism variances to get varied enough geological distributions.
elevation variance and range(with proper mesh size) is another fun thing to do with.
so you get many big enough moutain ranges, scattered neatly across the world, with apposite river start locations and erosion cycles. also it gives possiblity of waterfall, high cliff, shallow or deep soil in general etc.
combining with volcano and peak number tweaks and quite varied drainage/rainfall/savagery values, i could ensure a medium or small world has most features i could think of/dream about, that are normally occuring in larger ones.
too large rivers everywhere could potentially be a bane to FPS, but not too much unless you embark, like i did, on a convergence of three major rivers, with two waterfall, one 30 levels+, the other 10+ in a temperate forest that thaw half of the year. i abandoned it for every in-game year i had to wait four, five minutes, twice, for the water to freeze and thaw. horrible experience.
you could still get all three caverns and good amount of cotton candy whilst having a shallow world, that is to set [LEVELS_ABOVE_LAYER_1:#][LEVELS_ABOVE_LAYER_2:#][LEVELS_ABOVE_LAYER_3:#][LEVELS_ABOVE_LAYER_4:#] relatively low, [LEVELS_ABOVE_LAYER_5:#][LEVELS_AT_BOTTOM:#]with sorta arbitrary values.
and set[LEVELS_ABOVE_GROUND:50] like this would allow you to make a high tower basically 50 levels above ground. tried 120, not yet higher, but that was quite enough. actually i could not need more.