It depends on your environment and how much background noise affects your ability to focus. Earplugs with a 27dB noise reduction can be helpful if you're in a noisy setting, such as an open office, a crowded cafe, or during travel, as they can significantly reduce distracting sounds. If you find yourself struggling to concentrate due to external noise, earplugs with that level of noise cancellation could improve your focus by minimizing disruptions.
However, if the noise around you is relatively mild, you may not need earplugs with such high noise reduction. It really comes down to your personal need for a quieter environment.