So, Quark's Realistic Worldgen function is broken in 1.16.1. As far as I can tell, whenever the map is loaded from a save any chunks outside of what has already been generated has a chance of reverting back to vanilla world generation, leading to ugly and blatant chunk borders.
My current solution is to start a map in creative mode with maximum chunk distance and just manually loading as much as possible to ensure no broken borders generate. This has a few major issues, namely that it ruins any exploration I might want to do in the overworld for that map, it's slow and time consuming, and if I ever want to go outside of the area I generate there will still be problems.
Ideally, I'm hoping that there is a mod or tool compatible with forge 1.16.1 that will let me load and generate chunks within a wide area once automatically so that world generation can stay consistent after quitting. I don't really have my hopes too high, though.
Any help you can offer is much appreciated; I really don't like the vanilla world generation. As far as I can tell all of the other options for overworld surface changes are OTG presets, and they are all only in 1.12.2.
edit: Alternatively, if there's any way to bring back custom presets (which I understand were inexplicably removed in 1.13) I could just input the values that the Quark worldgen is based on.