I guess my question should have been - do most Pixel 4 owners manage on 64GB or is 128GB a must?
Yes, I manage and it took a little thought to realize it would be okay.
For my first Pixel, a 2XL, I got 128GB. Since then, I have done 64GB because I am finding I never use up the space.
I realized I don't need to keep every photo and video on my phone. In fact, by uploading to Google Photos, they are much easier to search through, lots of sharing options, and they are backed up. I can delete media from my phone once it's backed up. I do this all in original quality and pay $2/month for the storage (I use it for other things too). Totally worth it to me.
Then there's music... if you want to store a lot of music on your phone for offline listening (or not hit on your data), no way around it - you need physical memory. I don't. I have about 1.5GB of downloaded YouTube music playlists. Hundreds of songs. It works for me.
The "drawbacks" to my method are that I have to spend $2/month and I have to be a little more active about maintaining my photos/videos. I actually love it. I periodically delete photos from my phone once they are backed up. I delete all the crap photos and videos from my phone and Photos within a day or two of taking them, while I still remember what they were. Scroll searching through my photos/videos is easier because I deleted the multiple photos of the same thing, the terrible video of my class (but kept the good one I shot right after), etc.
I hover around 50% storage used.
As others have said, it's personal. Just tossing in another perspective. Sounds like you would need to start using photos backup more for it to work.