This is a great question. The photo ecosystem is one where I haven’t found a FOSS soln that hits all the marks of subscription services. I would focus on whatever helps you search.
I do feel like if files have accurate dates in the file system and in metadata, then folders based on event make sense.
However subscription photo services are very good at automatically sorting - these dates are holidays so these pictures are probably for that holiday. Your home location is here, these pictures are over there so this must be your trip to there. These pictures have these people or animals, so these pictures are about them.
With that comes seamless integration across devices - a picture taken at time now can be seen on a tv or laptop at time +x. Etc.
I have left the FOSS photo world but am definitely interested to see where it is. With digital photography finding pictures is the real trick. using folders like a tag hierarchy at least gets you in the ball park imo. But I have no practical knowledge any more.
Certain cloud providers are as secure, if not more secure, than a home lab. Amazon, Google, Microsoft, et al. are responding to 0-day vulnerabilities on the reg. In a home lab, that is on you.
To me, self-hosted means you deploy, operate, and maintain your services.
Why? Varied…the most crucial reason is 1) it is fun because 2) they work.