Ich kenne github.com/maybe-financ... und actualbudget.org (self-hosted Web Apps, keine native Linux App).
Anbindung an PSD2 ist halt schwierig ohne ne Firma dahinter, die eine BaFin Lizenz hat. Es gibt zwar goCardless, aber bin nicht sicher wie da das Pricing ist.

Maybe not the biggest, that depends on the other data, like video or images for example. But probably the one with the most rows/documents (whatever db you're using).

Sure the resource argument is a concern, but I think it only matters for really, really high traffic.

Yes, in general you would have a big table with all the events. But duplication of data depends on how you structure your events.

I'd say it was a good decision

Did you try out github.com/nikitabobko/... yet?