Each mod's ore generation is completely separate of each other, so if you want a similar amount of a specific ore generated, you will need to tweak the configs of the mod that's generating ores. Note that not all mods allow you to configure this, hence why in many FTB packs Thermal Expansion is used to generate the ores since it has a very customizable ore generation config.
As far as I know, Forestry and IC2 don't allow oregen configs; TiC does. Then again, there's Thermal Expansion, which has the most configurable oregen (and thus potentially produces the "most", depending on your config).
No clue to be honest. I hate to keep tooting TE's horn, but it allows configuring of the min/max oregen height, so you always know what height which ore generates on.
Another alternative would be Metallurgy3, but that would require even more tweaking and turning off of ores you don't care about in a "tech" environment. But then again, it provides amazing control of oregen.