Yes, I meant most suitable for you cache plugin, we have installed W3 Total cache, WPRoket plugin also is very cool cache plugin but it’s paid. If you prefer Fastest cache and that plugin has the option to combine scripts you can use it. But only 1 cache plugin, don’t use all of them at the same time.
1) W3 Total Cache has options for the JS and CSS minification and combination.
2) If you have responsive problems when using W3 CSS minification option then you need to find out which plugin or your custom styles cause this issue because I suppose even if you change the plugin you’ll get the same issue once enable minification.
W3 Total cache does not help only for SEO because this is the plugin not for SEO, this is the plugin to speed up the site.