i am a power user, and i have to use my phone all the time for work. so i do not necessarily follow typical protocol to extend battery life. i also tend to keep phones for no longer than 3 years (its usually two years). i have a car charger that i can connect to my phone, when my battery runs low. i also in and around hills that just ruins cell reception and thus really depletes my batteries.
so you have to think how long are you going to keep the phone? if not, then for how long(for me i might ditch my z fold 4 for the fold 5, if they include a s-pen slot which it is rumored to have). if it is not for very long, maybe no longer than a few years, then i would not get to crazy about 20% this or 80% that. for me i take my off charge at 100% and i come home. when i go to sleep i put my phone on charge, until i wake up the next morning....rinse and repeat.
but if you really want technical info about Li batteries and you have the time you can go here:
https://batteryuniversity.com/articles
it has a ton of info about them and teaches you the best practices for longer battery life. but i warn you they are not easy reads, but there is a ton of good info there.
now others here will chime in on what they do to keep a longer battery life.......but for me. i don't sweat the small stuff. i just plug and charge and go.