How to change the size of product variant and quantity drop down box and text spacing

Hello! I am trying to figure out how I can adjust the size of the drop down box for size variants on my product pages. Additionally, how can I change the size of the "quantity" box and the "Add to cart" button which is also not customizable for some reason. 

Lastly, I need to adjust the spacing between the product title, price and product description. You used to be able to easily customize this without code on the older Squarespace versions. I miss that time 😞 Can someone help? 

Site URL: https://www.quellcreates.com/store/p/babytee

@neswxyz you should be able to accomplish most of this with some custom CSS - can you be more specific with what you want for each adjustment? More space? less space? larger fonts etc?