Since 1.12, most of my favorite terrain generator mods haven't been updated, so I decided to take a shot at making a great custom preset for single player, cooperative and competitive play as a base world. I've nicknamed it the "superior" preset simply because it's not exactly realistic; I didn't really go for "realism" so much as a went for capacity: more distinction in biomes, bigger mountains, wider rivers, hills that are round, etc; an attempt to "amplify" the world without ending up with bubble-mountains. It's a modest success, from my playtesting.
Note that mineral settings are arbitrary on that, I've been using mods that disable vanilla oregen for everything but emerald.
I highly recommend adding Climate Control (Geographicraft) if you're playing forge, as it widens the rivers even more, gives you big beaches, and in particular it's nice to enable the banded climate (at something around 20--) since that will give you a certain direction to head to find cold or hot biomes. (It also avoids weird combinations that sometimes arise even with Minecraft's regular climate zones.)
Additionally, since Climate Control controls biome and river size, those options won't do anything anymore in the preset; make sure to set the Biome Size to 5 (half-way between "large" and "normal".)
In my screenshots here, I have a few other mods enabled; it gets pretty bulky.
Also interested to see anyone else's experimental results.
I just attached two further screenshots, which show what it looks like with Vanilla 12.2. I think the rivers may have some width issues, but I'm almost more impressed with the shape of the terrain.