My loafs so far/ sourdough crumb size

Hello everyone,

I have already introduced myself in another forum, but here is a brief recap:

I am a newbie to the world of sourdough baking and have only started experimenting with it a few months ago. I was mostly interested in creating a gluten free loaf that was as similar as possible to regular bread, due to my food sensitivities and I have successfully managed to create a close enough version. I have been also experimenting with regular flours such as whole grain and most recently spelt. In fact, as I am typing at the moment, I have a rosemory and olive spelt loaf baking in the oven! :)

I still have a lot to learn about sourdough, but one thing that I noticed with all my loafs is the close textured dense crumb, which I don't mind, but would love to see an open light crumb at least once. I am assuming the way to achieve that is probably to use a strong white flour at least partially in the recipe, which I have avoided to this point, or perhaps it is a result of the ratio of starter to flour used in a recipe. I would really appreciate some feedback from experienced bakers in here. How do you achieve that perfect crumb and rise in the oven. Thank you!