I gave up trying to figure out what reactor design would give me the right amount of steam & just picked a layout that one of the many tutorials I watched preferred. I went with a 7x7x4 reactor with 18 fuel rods (& 9 control rods) in a 3x3x2 in the center surrounded by gelid cryotheum (the passive coolant still gives you an efficiency boost in an actively cooled reactor). Setting 6 control rods to 90% & 3 to 100% dropped the temp down to just over 1200 degrees & dropped the fuel consumption rate to almost nothing (0.0018 0.017 mB/t, thought I might have put the decimal in the wrong place) while still outputting the 240 mB/t of steam needed to spin my turbine at ~900 rpm.
My turbine is a 7x7x6 with an 8 enderium block coil & 3 rotors with 8 blades each (24 blades total). Set at 240 mB of steam, the rotors spin at 996.2 rpm & produce 5218 rf/t (I altered this line in the config: D: PowerProductionMultiplier=2.0, the setting in the DW20 pack is 1.0, I think 1 of the vids I watched said the normal default is 1.66, & the guys on the Resonant Rise server had it cranked all the way up to 11.0).
With 24 rotor blades, I should be able to get 11 enderium blocks up to 1800 rpm w/600 steam. I think I can get that out of my reactor if I can get enough water flowing into it, but I have not yet tested this.