Hello @chainster_mike and welcome back to the forum!
Making these changes to DBC components is possible through cusom css in assets folder. You will need to find the right selector through developer console (F12) and place the change in your custom css. Example of this approach can be seen i.e. here: python - Styling Accordion tab dash bootstrap component - Stack Overflow. This applies the style for all components. If you want to apply it only for this one component you have to create css class and apply this class to your component.
From my personal experience I will recommend to have a look at Dash Mantine Components. I love creating these pixel perfect layouts and I prefer do it all in one place in python instead creating css classses. DMC has prop called styles API and you can access selectors directly from the components definition. I wrote a post about one problem I was trying to solve where I utilized styles API. Have a look here: dmc.Select and dmc.MultiSelect blended into the title using Styles API and PIL