When creating Yarn packages, you are encouraged to keep them small and simple. Break large packages into many small ones if it makes sense to do so. This is highly encouraged as Yarn is capable of installing hundreds or even thousands of packages very efficiently.
Many small packages are a great model of package management. Often this leads to smaller download sizes because you aren’t bundling massive dependencies and only using a small piece of it.
You should also consider the contents of your package. Make sure you aren’t accidentally distributing your tests or any other files that aren’t necessary for using your package (build scripts, images, etc).
Also be careful of what packages you are depending on, prefer smaller dependencies unless you have a good reason not to. Be certain that you aren’t accidentally depending on something massive.