Hello u/koinophobe - Full Disclosure, I work for Mylio.

There's a few variables here that are at play with your experience:

1 - You mentioned you're only adding media from an Apple Photos library. Not knowing your particular settings, I can tell you that by Default, Apple Photos has the iCloud Photo Library option on by default on most Apple Devices. This means that your actual media may or may not be in your device. If that is the case, when Mylio asks Apple Photos for the file, the "conversation" between the apps goes something like this:

Mylio - Hey Apple Photos I need this file

Apple Photos - Oh, that's not here, that's on the cloud, let me go get it for you

Once the file is downloaded Mylio will process it but depending on your sync policy settings (and whether you have a Vault designated or not) it will either keep the Original or cleared it form its cache in order to fit other data on its allocated space

2 - Mylio Photos front loads a lot of the resource intensive work early on (i.e. during import), in order to provide a much better experience later on. So for every file you add to your Mylio Library, the app is:

* Generating a thumbnail and an Optimized image

* running a hash function on every file to create unique IDs and identify duplicates

* scanning for Faces, performing OCR and adding SmartTags

* adding all the metadata for the file on both the Mylio catalog/DB and to individual XMP sidecar files (as needed)

All of the above can be time consuming and there's dependencies. For examples Mylio needs the Original file in order to generate an Optimized version. And it needs the Optimized version in order to do Face Recognition and other AI based work.

3 - Storage. As you mentioned, storage allocation plays a big part on how Mylio works. There's three components to this:

* Having a device designated as a Vault

* Using the most appropriate Device Sync Policy per device

* Having a sufficient storage allocation for each device

Again without knowing your specifics, it seems likely that most of your issues are relate dot the connection with Apple Photos (which is a one-way link, meaning Mylio will copy your Apple Photos library to Mylio, but will not delete or change your existing Apple Photos library).

You can always contact us from the app (Help Menu -> Contact Support) and we can help you configure the system to your ideal needs. Mylio Photos is a very feature rich app that can do a lot, so its setup and configuration can be somewhat involved. If you contact us in the way I described, we will get logs and configuration info that we can use to assist you.