Devil Fruit Boxes
Devil Fruit Boxes are the main way of obtaining Devil Fruits in the mod, they're found in chests in various mod and vanilla structures.
Devil Fruit Boxes come in 3 categories which also denote how rare or powerful the fruit inside will be.
Wooden Box: 22 fruits
Iron Box: 31 fruits
Golden Box: 19 fruits
All Logias will be inside the gold boxes along with strong paramecias or mythical zoans.
Every box has a 5% chance to be empty, however they also have a 5% chance to contain a fruit from the next tiered box (obviously with the exception of gold boxes). This means that you can obtain logias from iron boxes as well, just at a very low drop rate.
Other than that every fruit has an equal spawn % based on how many fruits are in their box.