Thanks for writing in!
1.To change default site link colors, please head over to X -> Theme Options -> Typography -> Site Links section.
2.To remove the line under navbar, try adding the following CSS rule into your X -> Theme Options -> CSS area.
3.You can increase base font size within your Accordion element.
To change fonts, please review our Font Manager guide (https://theme.co/apex/forum/t/font-manager/101) and set a font that you would like. Then you should be able to access it within Header tab of Accordion element and set the font.
Hope that helps.