If you've set yourself as both a player and game developer, it's possible to make blog posts, and then place links to those posts on your profile page.
In this case, you can post your writing on medium as the link.
Try https://itch.io/user/settings
And yes, you can absolutely customise it with CSS. But you'll need permission from the itch moderation team to do so.
As for your writing, I'm not too sure I actually understood your intent.