Personally, I think the 80% charge limit is a gimmick, which won't make your battery last any longer. Most of us, who have been on this forum for years, use Optimized Battery Charging, with our phone plugged in to charge when we go to bed, leaving them on charge all night, EVERY night. We wake to a fully charged phone, which lasts throughout the day. Next, your phone is new (only a couple days old) and new phones take a few days to index the millions of bytes of data on them. Battery life with a brand new phone usually is diminished for a while until all the data is indexed. Plus, while it's working in the background, you are likely testing things out, such as playing games, listening to music, taking photos, etc., all of which are battery intensive all by themselves.
Keep in mind that Battery Health is more a function of charge cycles. If you charge to 80%, you'll likely charge it more often, and a charge cycle is how often you charge from 0% to 100% or fractions of charge cycles which amount to 100% with multiple charges. For example, charging from 50% to 100% is 1/2 a charge cycle. Charging it again from 50% to 100% a second time equals 1 charge cycle. So the charge limit really won't do anything (in my humble opinion) for you.
I have charged my iPhone 16 Pro Max to 100% every night since I got my phone on Launch Day, last September and my Battery Health is still at 100%.
