These are modular, compatible packages so you can pick and choose what you want.
1. No Breeding Cooldown
You can now breed your champion bloodline stallion to all of your mares in the same day. :)
2. No Relationship Needed for "Encourage to Breed" request.
This will make it so the minimal requirement to ask horses to breed is having met the horses you are asking. However it may take more than one attempt (typically 2) for a horse you have no or a poor/negative relationship with to cooperate. They will eventually complete the request with consistent asking- but you can always increase your relationship to make it much easier.
A very nice use of this is for making a 'stud farm' family. Tip: You can add the champion trait/gene with MC Command Center and it will breed down the champion bloodline so you don't have to grind levels or waste time adjusting them with MCC. Now you can visit the stud farm with your mares. I like to envision a stud fee and use money # to change my simoleons lower to 'pay' the fees I have mentally set. :)
3. Better Champion Gene
I find the vanilla Champion Gene trait to be very underwhelming and barely noticeable. This mod increases the current modifier from x1.25 to x2.0 in all four horse skill gains.
4. Champion Gene Trait Sells for More
A multiplier that applies AFTER the game has gone through other multipliers to determine your horses value. Comes in x2 and x1.5 flavors. Only use one of these two files! For example a newborn without the trait would still be 1k, but a champion with x2 multiplier mod would be worth 2k at birth. At FULLY TRAINED (10 in all stats) horses are worth around 20k. Which would make it 40k with this mod.
---Install---
Unzip with 7-zip/similar. Open the extracted .packages files and paste it to Documents\Electronic Arts\The Sims 4\Mods.
You can pick and choose which ones you want to use, but for #4 there are two files in its respective zip and you must choose ONE version to use. (x2 or x1.5)
Optional: You can place it inside a folder in Mods also, but only 1 level deep.