With some simple signal routing, Cubase can tell you exactly what a plug?in is doing to your audio.
A limiter's primary function is to prevent the loudest signal peaks from exceeding a specified maximum level, but they're often also used as a 'maximiser' to increase loudness — as you raise the input signal, everything below the limiter's peak detection threshold gets louder, while the peaks are reduced to the threshold level. But the latter tactic can mean the limiter both acting more frequently and applying more attenuation, and the more you ask your limiter to do, the more unwanted sonic artifacts it will leave behind. Eventually, it will become audibly unpleasant.
You can't simply crank up the gain and hope for the best, then; you must train yourself to hear exactly how the limiter is changing your audio. When you overdo it significantly, it's very easy to hear any damage being done. But, especially when you first start experimenting with limiters, it can be harder to judge where the sweet spot is.
To make this a little easier, you can use a technique that's often referred to as 'delta monitoring'. Essentially, this requires you to subtract the processed signal from the unprocessed one, so that you can listen to the remainder, which is what your limiter is removing. Some third-party plug?ins helpfully include delta...