Hi,
1. Well not exactly like that, but there is a priority groups feature, that may help you achieve something similar. You cannot hand pick the results for phrases, but you can prioritize some matches over others.
2. You might have a CDN (like cloudflare) + Minify cache enabled + Browser page cache, so the browser may serve previously cached pages (wich is the main purpose of cache) with minified files that no longer exist when the cache is cleared.
From the plugins perspective there is nothing I can do about it, as the plugin stylesheets are registered just like any other ones, it is up to the cache solution to handle them. Usually clearing all layers of cache one after the other should do the trick.