You can have Experiments running on client side (JS) without redirect to different versions of the page, but setup process is... strange to say the least - https://developers.google.com/analytics/solutions/experiment...

Still, after setting it up it worked just fine for us.

Also, I have yet to figure out how to run multiple experiments on the same page (rather than multivariate single experiments). Usually frowned on, but when you're testing a new search box site-wide and different CTA buttons, they're discrete tests.