Hopefully I can share some useful information for others tying this for the first time.
When I started uploading the photos to the cloud from my mac (10,000 of them), the pics started appearing in the cloud relatively quickly. They also started downloading to my phone pretty quickly. However, none of the photos were going into my albums. The empty albums appeared, but the photos that should've been in them were all appearing in only the recents album.
The upload seemed to stall out after 36 hours so I signed in and out of the cloud, rebooted my computer, and made sure the hard drive never went to sleep. I don't know if this helped but it couldn't hurt so I did it. I contacted apple support at this point and was told that I'd have to reorganize the photos into albums again. This is contrary to everything I read about how this should work and the thought of sorting 10.000 photos wasn't very appealing so I rejected their advice and escalated the issue within apple. The next support person agreed that this didn't appear correct and agreed to contact engineering support and follow up with me the following day.
At one point that evening (40'ish hours into the process) the photos app started showing the message "collating data" (or something along those lines) where it had previously shown "uploading". It seemed to stall again so I rebooted again.
My mac crunched away overnight and when I checked my phone one morning, all the photos were in the correct albums! My best guess is that the photos didn't get assigned to any albums until the very end of the process. This happened before I got any further feedback from apple support so I didn't follow up with them to verify if this is correct.
I'm currently trying to sync my iPad and its been over a day so far, but it looks like patience is the key to success so I'm going to let it run longer before I look for more support. FYI, I have a fast internet connection so that wasn't a factor in how slow this was.
