I'll be completely honest, after having played this for a few days, the balance on this mod is really frustrating. To me, it feels like you're punished for engaging with the main mechanic and it feels really really bad. It bothered me so much that I felt the urge to suggest reworks for nearly a third of the cards (and at least one core mechanic) that actually make them rewarding instead.

This mechanic does not need to exist as its own stat.
Buxom turning into Bounce does nothing but confuse the players and obfuscate an otherwise simple mechanic. It would be much simpler both for the player and mechanically if it were just worded as "Creates a bounce status card in your draw pile for each time your buxom goes over the [insert better name here] limit"

More frustratingly: None of the cards engage with the Bounce status cards well. The moment you start generating more than 2 status cards in your discard pile per turn you start losing your ability to draw the cards you put in your deck with no upside. This is because they are generated every single turn with no counterplay.

There are three very obvious solutions to this issue:
1 - Change the starting relic. Capacity just isn't as integral to the playstyle as being the starting relic implies.
Instead of providing capacity, guarantee that the player will always draw at least 1 non-status card at the beginning of their turn. This will greatly off-set the downside of generating such a ridiculously gigantic number of status cards without completely ruining the balance.

2 - Make card draw way way way better. There're two ways to do this, and frankly you'll need to sprinkle a bit of both on each of them. Card draw should be equally split between guaranteeing that you draw a specific kind of card (non-status, power, skill, attack) or if it's more general it should have retain. This character generates too many status cards for the draw cards to not be either specific, retained, or both.

3 - Make more ways of increasing the bounce limit. There just isn't enough interplay with this limit, as right now there's only one card that increases the bounce limit and it's a power. Both high buxom and high capacity builds are greatly kneecapped by the sheer bulk of status cards that are added and without a way of decreasing this it makes those builds incredibly difficult to run with.

With that out of the way, it's time for me to propose my reworks:

Omegabsoption - Basic should already draw 2 cards. Upgraded should gain retain. As-is, the card's value is kneecapped by how many status cards the character generates, and it just doesn't feel powerful enough given that. By increasing the base card draw and giving retain when upgraded it allows for keeping the same synergies without greatly upsetting the balance.
Bra Closet - Should guarantee a draw of 2 non-status cards. To me it feels like if this card is going to exhaust that it's better to give it a little more value than to just give it basic card draw because it just never feels like it has the value it should have.
Brain Drain - Add Retain.
Omega Bonk - Remove gaining bounce, instead have it inflict 2 damage on the player for every status card currently in hand. This keeps the riskiness of the card without the annoyance of adding yet further status cards. Plus it gives a chance to synergise with other mechanics like status removal. As is it only contributes to the frustrating amount of status cards, which just don't have enough ways to draw/remove them.
Panic Lactation - Upgraded should change the energy cost to 0 instead of adding 1 milk gain. It's almost never worth playing this card as is because it just doesn't generate enough milk to ever be worth it, the energy cost being changed allows it to be a less risky card on runs where you have 3 or fewer energy and overall increases the value.
Watcher Cosplay - Lower energy cost by 1. This in theory should be equivalent to Bouncing Lactation but the exposed synergy allowing for extra damage doesn't make up for how little milk gain it provides by default. This change increases the card's value across all deck archetypes.
Chibi Offering - Make common. Lower milk gain to 6 when basic, return to 10 when upgraded. This card is essential for exposed runs, and being uncommon kneecaps that build and makes it significantly more difficult to play.
Hardheaded - Upgraded should gain retain.
Malfunction - Upgraded should gain retain.
Pop, Pop, Pop! - Should guarantee drawing non-status cards.
Bovine Form - Missed potential. Replace "Gain 10 Lactating" with "For the rest of combat, any block gained becomes milk gained." The original was just incredibly low value for the energy cost because it's essentially equivalent to a decreasing block each turn. Even assuming that a monster doesn't attack for a turn you're only getting 19 temporary hp, and this decreases over time. With my change it becomes a much higher value card and better justifies the 3 energy cost without becoming too powerful.

I really do enjoy this mod (and not just because of the lewd) and it feels so close to being just as fun as it is ~"engaging", and the amount of effort that was put into it is apparent from the moment you start playing. It's why it felt so frustrating to me that the balance is so shaky. I don't want that effort to be wasted by under-powered cards that don't make up for the status mechanic's downside.