Fonts and sizes and other stuff help

Is there a stack that allows me to change the fonts, colors, and size of the fonts any web page that I build that can be integrated into Rapid Weaver?

My current site is www.fresnoflyfishers.org and I used Sandvox for it, I build a test site using Rapid Weaver at www.fresnoflyfishers.net

My board likes the Ariel Theme and size 18 since many of them are older and like to be able read the site where more of the modern sites they can’t see that well. They like the look of the Sandvox site however with Sandvox I am limited on what I can do. I have stacks 3 and used that to build the test site, however when using the stacks I am unable to select the font or select sizes of the font.

What I like about the sandvox is that I can throw in a banner that will go across all pages and I can use a slide show on any page and it is easy to implement. Is there something similar that I can do for RapidWeaver?

I liked the site that I used for the test site but want to have a bit more control than I have now. Is there any stacks that allow me to do this that work with Stacks 3?

I am doing this as a hobby and not a business that is what makes Sanvox so easy to use, however I know that in order for my site to look better and have more functionality, I have to make the change. Any help would be appreciated.

The free Fontstack from https://stacks4stacks.com/fontstack/ will let you add Google fonts to your site which is a good place to start.