1. It is very likely due to the site cache/CDN cache and local browser cache inconsistency, the plugin has no impact on it. I recommend turning off the cache until development, as caches are to perserve a static state of a page. Breaking design could mean that parts of the CSS were parsed from the browser local cache (or an older CSS file was automatically parsed, depending on header configuration), from a state when the plugin was not active. From the plugins perspective, there is nothing I can do about it unfortunately. The CSS files are enqueued properly via the recommended methods, so the rest is up to the caching solution. When making changes, I usually reload my browser cache and hit CTRL + SHIFT + R to clear the local cache during reload as well.
2. You can change the magnifier and return button events and the results page URL on the General Options -> Logic & Behavior panel: Documentation – Return key and magnifier icon click actions
That is probably what you are looking for.
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