Look at the normal preview how much resource there are and then look at the islands. The frequency makes more ore patches so you can scale it to get the same number of patches in both cases.
Or you can increase the size so the fewer patches you have on islands are larger and have more ore. (Or did that actually just spread the same amount wider?)
Or as third option you can increase the richness so each ore patch has more ore and lasts longer. But you can't mine it any faster.
I would try 200% on everything and see how it goes. On the other hand bitters are hit by the same effect as ores. So you get less of them too. And if they can't swim they can't attack you making things even easier (except landings). If you like long train rides then you could just leave everything default and enjoy long ship travels. Just pick the islands with resources.
