Esper's senior technical editor Mishaal Rahman said that if you have a 128GB phone you could lose half your storage for the Android OS and packed-in apps. That's four times the size of the normal Pixel 7 Pro system partition, which is 15GB. It's the size of two Windows 11 installs.
It is hard to imagine that Samsung has packed your phone with some good coding which you need. Most of the changes might be geared to propping up an appearance of being a non-Google ecosystem and it clones every Google app that comes with its devices. This is pointless as Samsung is contractually obligated to include the Google apps, so you get both. This means two app stores, browsers, voice assistants, text messaging apps, and keyboard apps. Since these are installed in the system partition they are tricky to remove.
Unlike the clean OSes you'd get from Google, Samsung sells space in its devices to the highest bidder often with toe curling settings. Facebook can buy a spot on Samsung's system partition, where it can get more intrusive system permissions that aren't granted to app store apps.
Netflix, Microsoft Office, Spotify, Linkedin are all there too. To make matters worse the carrier will install their own crapware too. The average amount users are reporting is 60GB, but it could be a lot worse.