Charging iPhone 15 Pro Max

I'm about to buy an iPhone 15 Pro Max and I have a couple of questions. Will charging the phone at 5W instead of 20 allow me to degrade the battery less over time? I also tried on my iPhone X and heard that on a single charge charging it at 5W will allow it to discharge less quickly than with 20, could this be possible? So if charging it at 5W is a better option (I would always only charge it at night so the speed doesn't matter to me) and I have a 5W Apple charger for iPhones I just need to find the USB to USB-C cable. Do you have any advice? Is this one from UGREEN any good? Because I also saw that not all cables are the same. Thank you