I was also worried about the same issue. However I have the 32gb first gen pro. I was able to get by with that so I’m thinking that I’ll save the money and go with the 64gb. I have cloud storage from both one drive and iCloud. The only thing I would really need the storage for is for photos. But with cloud storage it pretty much helps alleviate that issue.
Same exact story: the extra would be just for photos. I wouldn’t end up backing them up on an external hard drive (if iOS ever allows it) since I travel a lot so I can’t think of any other reason to go higher than 64GB.