It's me again. After all, this mod has a strong correlation with the EnvironmentZ mod.
After trying the latest version, I found the following problems:
Firstly, there is no direct purification method for the flasks, which makes flasks meaningless in front of stackable bottles.
What's more, the purified water formula provided by the brewing stand has no use on the flasks.
Secondly, when there is a stackable mod, adding water to the campfire cauldron with bottles will cause the stacked bottles to become one.
Finally, when the purified water is poured into the campfire cauldron with the campfire not lit, the water will be unpurified.
Above, I hope my test can help you improve the mod.

I also found that the diamond leather flask and the netherite leather flask had the same capacity.

Finally, when the purified water is poured into the campfire cauldron with the campfire not lit, the water will be unpurified.

NAB. Please post each individual bug separately next time, it would be much appreciated.

We will resolve this issue and might look into making purification a blockstate system (undetermined).

Actually no need to open multiple issues :)
To get purified water, you have fill the flasks or bottles at the campfire cauldron which now takes 5 seconds by default to get purified when the fire is lit. I actually don't care too much about the stackable mod because in my opinion it's op but the latest update may fixed this bug. As far as I know, you can fill the cauldron with purified water?
The netherite flask has intentionally no bigger capacity cause it's fire resistant :)