Your iPhone acts as temporary storage these days. It should be used to hold current photos, files, videos and music. Everything that's not "current" should be purged from the iPhone and left on iCloud. You can then pull it back if/when you need it.
This is all done automatically for you using the "optimise phone storage" options for Files, Photos and Music.
In short, if you have iCloud storage, then 64GB should be more than enough. If you don't, then go 256.
The exception to that is if you record a lot of video and are hoping to use 4K@60, I might also suggest 256GB since you need more 'temporary storage' before it's offloaded to iCloud. 4K footage comes at a storage cost.
Of course, if the money doesn't matter to you, then more is always nice. And some people like to have everything stored on their device at all times, not just held in the cloud - that's fine too.