Just to make it easier to keep track when things stack additively or multiplicatively. +10% and +10% give +20% for the same source and +21% for different sources, but it's not always clear when two things are "the same". Leveling up your mastery of a spell gives you a bonus that stacks additively with leveling up other spells. And, sure, of course it does, because of the intermediary, but I still want that explicitly laid out somewhere. Does two different sources of resource quality giving +1% and +2% stack to +3% or +3.02%? If I have two different charms boosting the same thing, are they additive (because they're both boosts from charms) or multiplicative (because they're different spells)? What about if I have two copies of the same charm up at once? Does the exponential upgrade boost apply to the levels you already have, or only to future purchases?
I could go on for a while, but I'll stop here. I don't actually want you to answer these questions; they're representative of the ones I have, but by no means comprehensive. I want the answers to these questions to be somewhere in the game (probably hidden behind some menu to not get in the way). I want to be able to ask the game how it gets its answers and follow along.
... also on the topic of "option to make things more visually complicated", it'd be nice if there was a setting to make everything start at 0 instead of 1, so that level n means a +n bonus instead of +(n-1).