You’re right about the artwork. Generally, when transcoding, no artwork is being transmitted.
The “DB version” doesn’t have anything to do with the backend, unfortunately. But 2 is alright.
Well, if it’s all flac, then I assume that the transcoding plays a part in this.
Maybe it is iTunes that tries to prefetch album art and then firefly has to do transcoding – I don’t know. But it’s very likely theres a connection between the transcoding and the cpu spikes. 😉