Gamespot talks about how massively the expansion changes the core systems of 2077 and their impressions of the general story of Phantom Liberty. Here is a snip;
What's most impressive is how different Phantom Liberty feels compared to the vanilla experience and how these changes could breathe new life into the core experience. Nearly every system has been touched up or redone, and new mechanics have been introduced, such as car combat–and these features aren't limited to Phantom Liberty.
For example, cybernetics received a complete overhaul. Now, armor is tied to your cyberware rather than clothing. This means you can wear whatever you want without worrying about your overall defense and combat effectiveness. However, you can't install a bunch of cyberware at once. As you progress you'll increase your cyberware limit, and if you install too much you'll be hit with various debuffs. Not only that, but when you install new cyberware, you'll get to see the installation process from V's point of view. While we didn't get specific examples of how cyberpsychosis could affect your character, getting debuffs from excessive cybernetics fits within the context of the world. It seems like a much more refined system that will force players to carefully pick and choose cyberware that fits their play style.