I'd like to be sure I understand what you are saying and seeing, and that when you compare with your wife's device you are comparing like with like. There are a couple of things that make me unsure:
1) you talk about overnight losing 3% per hour, in which case if your 30-45% refers to that then it means this thing is using 1-1.5% battery per hour. If your 30-45% is averaged over a whole charge cycle then what it means in terms of actual usage will depend on how heavily the phone is used. And is that 30-45% of total battery use, or 30-45% of the usage by apps (different things, since apps are far from the only things using power)?
2) when you say "same 30-45% of battery usage is shown under the settings app" what exactly do you mean? Do you mean that if you look in settings you see 30-45% of usage being attributed to Device Care (in which case what is the other thing that's telling you it's using this much)? Or do you mean that something else is telling you that Settings is using 30-45% of power? It's not clear to me, I'm afraid.
Different apps measure power usage in different ways, so you might want to try a third party app (e.g. GSam Battery Monitor) to get a second perspective on how the power is used.
Frankly if it were even averaging 10% of overall power use (with my usage pattern, where the phone is frequently used rather than left on standby all of the time) I would disable it. It's not a necessary part of Android, it's something Samsung added to their ROMs. I don't have any device which has this app, and haven't missed it or felt the need to find an alternative, so if I bought an Samsung and decided it was a significant power drain I'd just turn it off.