A repack might include fixes for bugs or issues that were present in the original release, offering a smoother gaming experience.
If you want to experience the game fully and stably, buy the legitimate copy.
Returnal launched with Denuvo, a controversial anti-tamper software known for causing performance stuttering. While the official version still requires Denuvo (which constantly writes data), cracked versions found in repacks remove Denuvo entirely. Many players report that the repacked version runs smoother than the legitimate copy because the CPU isn't busy checking DRM every millisecond.
The PC version is considered an exceptional port by critics at BGeek and GameSpot , offering several technical upgrades over the console version. Returnal™ on Steam