I've put most apps to deep sleep mode in the battery/background usage settings. Really don't want anything doing stuff in the background unless I want them to or system related process. Also, switched back to 4G and only activate 5G if I really need the speed for something, it saves a lot of battery. I find it that the battery drops back to the high eighties fairly quickly but then it really slows down.
Pretty much all Samsung phones I've owned don't stay at 100% after charging for long. Typically you'll see a fairly steep drop at first but drain will normalise and drop much more slowly later on. If you were just texting for 49m straight and lost 7% that's pretty much as expected of SoT which at that rate would last you well over 11h.
the battery will always try to balance out the positive and negative charges meaning that 50% is the most efficient % to keep your phone on because it will last longer + will do less damage to the battery in the long run