I have been spending the past three days trying to find mines in worlds. I have tried the easyretrogenmod, which doesn't seem to work.....
So I HAVE seen railcraft ores, but they are only a few blocks; sometimes even one. In a continue to my trial and error, I went into config and set all the ores to DIFFUSE. After I did this, I started seeing nickel and zinc in caves pretty often, but the confusing part is I also found what LOOKED like iron mines. I double checked and the setting was indeed set to diffuse. Now this MAY be a complete coincidence but I created several worlds in default config where I could only find a couple ores around.
I am playing the latest version of railcraft for 1.12.2 and Forge 14.23.5.2838

Mainly I would just like to know if mines are for sure generating because I don't want to continue my effort digging in my survival world if they aren't.

update: So I found skygen and turned it on. How often are you supposed to see ores? I flew around a lot and couldn't find any..... unless a) theyre really high in the sky or b) skygen is broke