I watched a few videos which said that slow charging my iPhone at 5w is the way to reserve my battery health and keep it at 100 percent capacity for at least a year. They also said fast chargers or super fast chargers ruin the batter health, and I recently bought the vellum 30 W charger so I’m not really sure what to do and what to charge my iPhone with to keep my maximum capacity at 100%
To expand on edclange's excellent advice, you can read here:
When to charge your iPhone or iPad - Apple Community
Remember that, no matter what you do, your battery capacity will drop and, eventually, the battery will need to be replaced. That is normal and expected.
Most of what you can read or watch about iPhone charging practices is wrong. Especially if you saw it in a video. Those videos are there to make someone money. And especially stay away from advice that tells you to unplug your iPhone when it charges to 80%. Don't trust anyone or any site that tells you that.
Let your iPhone handle its own battery. It can do it better than you. Turn on Optimized Battery Charging, plug in your iPhone overnight to a good quality charger (any wattage), and don't worry about it.
iPhone 15 pro battery health capacity
