Hi, performance wise, should I activate extra models of the theme to adjust (let’s say colors) or do it from from CSS?
In other words, do activate extra models of the themes (if not needed or can be done elsewhere) affect the performance?
if the option is available in the Customizer then you should use those settings. They simply output those styles within the same style sheet as the other theme settings. This makes them more performant although the difference in speed would be unnoticeable.