Looking at the chemical plant it has 3 fluid inputs. The fluid boxes for it have an base_area of 10, 10 and 2.

Why are they so different? Makes the plant buffer different amounts of the fluids and the recipes (like graphite) seem to use more or less the same of each.

The beavior I see makes even less sense now that I looked at the values. The effect I see is that for example carbon monoxide buffers 5.5 carbon dioxide but over 213 hydrogen and still rising. (All my fluids are 1/10th from another mod because it balances fluid wagons better, so this should be 55 and 2130 without that mod). But hydrogen is the fluid connection on the side, the one I believe is smaller than the others. So why is the smaller fluid box buffering fluids all out of proportion?

It seems the first two fluid inputs are limited by the recipe while the third fills up to the full size of the fluid box.

The chemical plant's side input is flow through, for more compact layouts. So you can connect a whole row of chemical plants adjacent to one another with only a single pipe connection to one of them. The other 2 inputs are purely input, but that one is input-output.