There is no "size rule", but there are good principles for both proportion and for illumination.

Some folks like "decorative" light fixtures, sometimes called chandeliers. Some folks, like me, don't like light fixture which call attention to themselves and attempt to dominate a space. Pendants can be large, complex and visually strong...or they can be small, simple and unobtrusive.

Pendants can be clear and transparent, or they can be metallic and opaque.

Thus, it's virtually impossible for anyone here to give you a definitive answer to your question, especially without seeing your house, the interior space and furnishings.

If you are having trouble figuring out all of this, why don't you pay a designer for an hour's time and help you select pendants which will be workable and in good taste for the style of architecture of your house?

We are going through the same decision. I agree with Virgil that the "right" size depends on several things and there is no right or wrong answer without taking the space into consideration. A visually heavy pendant/mini-chandelier, maybe just two, but light and airy chandeliers, maybe three.

Here are a couple of helpful links:

https://kathleenjennison.com/2015/how-to-pick-a-perfect-pendant-light/

https://blog.yaleappliance.com/how-many-pendants-do-you-hang-over-a-kitchen-island