I have not much to say here other than I use an iPhone XR 128, new, from about a year after it launched in 2018, and it still runs fine. Fairly heavy user, battery health is at 89% (Settings/Battery) after two years and that’s generally OK, but on heavier use days, it is noticeable.
64 GB Storage will be fine for most mainstream users, even if you keep a of photos and apps on your phone, if you have “optimize phone storage” turned on in Settings/Photos. This keeps a lower resolution copy on your phone and the full resolution original is in iCloud. When you click on a photo, the full resolution photo downloads automatically. If you like keeping the original resolutions on your phone, 128 GB storage might be a better choice.